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RESEARCHES OX FtJXGI
RESEARCHES
ON FUNGI
AN ACCOUNT OF THE PRODUCTION, LIBERATION,
AND DISPERSION OF THE SPORES OF HYMENO-
MYCETES TREATED BOTANICALLY
AND PHYSICALLY
ALSO SOME OBSERVATIONS UPON THE DISCHARGE AND
DISPERSION OF THE SPORES OF ASCOMYCETES
AND OF PILOBOLUS
BY
A. H. REGINALD DULLER
B.Sc. (LoND.) ; D.Sc. (BIRM.); PH.D. (LEIP.)
PROFESSOR OF BOTANY AT THE UNIVERSITY OF MANITOBA
WITH FIVE PLATES AND EIGHTY-THREE FIGURES IN THE TEXT
LONGMANS, GREEN AND CO.
39 PATERNOSTER ROW, LONDON
NEW YORK, BOMBAY, AND CALCUTTA
1909
67S38
All rights reserved
toi
TO
WILHELM PFEFFER
UNDER WHOSE STIMULATING GUIDANCE
THE AUTHOR ONCE HAD THE
PRIVILEGE OF STUDYING
PREFACE
THESE pages contain a contribution to the physiology, mor-
phology, and physics of reproduction in the Hymenomycetes, and
also a record of some observations upon the discharge of spores
of 'Ascomycetes and of Pilobolus. Naturally many problems have
^ been left unsolved, but I hope that the new data obtained will
\^ give an added interest to some of our commonest plants. The
delicate adaptations of structure to function, as revealed by a
study of the fruit-body of a Mushroom, a Coprinus comatus, or
^ a Polyporus, have provided me with no small cause for wonder-
^ ment and delight, and they seem well worthy of the attention
^' of all those who desire to understand more fully the vegetable
world by which they are surrounded. The value of the more
purely physical work must be left to physicists to decide. How-
ever, as showing how closely the various branches of science may
^ be knit together, it is not without interest that the first direct
V test of Stokes' Law for the fall of microscopic spheres in air has
. been carried out with the help of a lowly Cryptogam.
The research, which has occupied five years, was preceded and
'N suggested by a systematic study of fungus species in the field, in
which I was much assisted by Geo. Massee's British Fungus Flora
and M. C. Cooke's Illustrations of British Fungi. During the
winters the experimental work was carried on in my own laboratory
at the University of Manitoba, and during the summers in the
Physics and Botanical laboratories at the University of Birming-
ham. I have much pleasure in expressing my best thanks to
Professors Poynting and Hillhouse for the facilities accorded me.
I also wish to acknowledge my indebtedness to Dr. Guy Barlow
viii PREFACE
for valuable help and criticism in the more purely physical
and mathematical parts of the research. Of the photographs here
published ten were kindly made for me by Mr. J. E. Titley of
Four Oaks, Warwickshire, three each by Mr. J. H. Pickard and
Mr. P. Grafton of Birmingham, and two by Mr. C. W. Lowe of
Winnipeg. They are all acknowledged in the text. In the final
revision of the proofs, Mr. W. B. Grove has been good enough to
give me the benefit of his wide mycological knowledge and experi-
ence. Lastly, my gratitude is due to the Birmingham Natural
History and Philosophical Society for defraying the cost of three
of the Plates.
A. H. REGINALD BULLER.
WINNIPEG, July 1909.
TABLE OF CONTENTS
PAGE
PREFACE vii
PART I
Ax /ACCOUNT OF THE PRODUCTION, LIBERATION, AND DISPERSION OF THE
SPOKES OF HYMENOMYCETES TREATED BOTANICALLY AND
PHYSICALLY
INTRODUCTION .
CHAPTER I
The Hymenium Basidia and Paraphyses Nuclear phenomena The Colour
of Spores Two-spored Basidia in Cultivated Varieties of Psalliota cam-
pestris Occasional Sterility of Coprinus Fruit-bodies Cystidia Fungus
Gnats, Springtails, and Mites Position of the Hymenium Comparison
of the Basidium with the Ascus The Effect of Sunlight upon Spores . 6
CHAPTER II
The Extent of the Hymenium Principles underlying the Arrangement of
Gills and Hymenial Tubes The Margin of Safety The genus Fomes . 27
CHAPTER III
The Functions of the Stipe and Flesh of the Pileus The Gill-chamber . 39
CHAPTER IV
Adjustments of Fruit-bodies in the Interests of Spore-liberation Lentinus
lepideus, Psalliota campestris, Polyporus squamosus, Coprinus plicatilis,
('oprinus niveus, and Coprinus plicatiloides Reactions of Fruit-bodies to
Light and Gravity The Problem of Pileus Eccentricity Geotropic
Swinging Rudimentary Fruit-bodies 47
CHAPTER V
Spore-deposits The Number of Spores 79
CHAPTER VI
Macroscopic Observations on the Fall of Spores of Polyporus squamosus . . 89
x TABLE OF CONTENTS
CHAPTER VII
PAGE
The Demonstration of the Fall of Spores by means of a Beam of Light . 94
CHAPTER VIII
The Spore-fall Period . . . .102
CHAPTER IX
Desiccation of Fruit-bodies A Xerophytic Fungus Flora The genus
Schizophyllum 105
CHAPTER X
External Conditions and Spore-discharge The Effect of Light The Effect
of Gravity The Effect of the Hygroscopic Condition of the Air The
Effect of Heat The Effect of Alteration in the Gaseous Environment
The Effect of Anaesthetics 120
CHAPTER XI
The Violent Projection of Spores from the Hyraenium Methods I., II., III.,
IV., and V 133
CHAPTER XII
The Mechanism of Spore-discharge . . 148
CHAPTER XIII
The Specific Gravity of Spores . 153
CHAPTER XIV
The Size of Spores Poynting's Plate Micrometer 158
CHAPTER XV
The Rate of Fall of Spores and Stokes' Law Appendix < . . . 164
CHAPTER XVI
The Effect of Humidity on the Rate of Fall of Spores 179
CHAPTER XVII
The Path of the Spores between the Gills, &c. The Sporabola Appendix
on the Motion of a Sphere in a Viscous Medium, by Dr. Guy Barlow . 184
TABLE OF CONTENTS xi
CHAPTER XVIII
PAGE
The Electric Charges on the Spores 192
CHAPTER XIX
The Coprinus Type of Fruit-body .196
CHAPTER XX
The Dispersion of the Spores after Liberation from the Fruit-bodies
Falck's Theory 216
CHAPTER XXI
The Dispersion of Spores by Animals Coprophilous Hymenomycetes
Slugs and Hymenomycetes . . . . . . . . . 224
PART II
SOME OBSERVATIONS UPON THE DISCHARGE AND DISPERSION OF THE
SPORES OF ASCOMYCETES AND OF PlLOBOLUS
CHAPTER I
The Dispersion of Spores by the Wind in Ascomycetes Puffing The
Physics of the Ascus Jet in Peziza The Fixation of the Spores in the
ASCIIS of Peziza repanda Comparison of the Sizes of Wind-borne Spores
in Ascomycetes and Hymenomycetes The Helvellacese .... 233
CHAPTER II
The Dispersal of the Spores of Ascomycetes by Herbivorous Animals illus-
trated by an Account of Ascobolus immersus Pilobolus, Empusa muscx
Lycoperdon The Sound produced by the Discharge of Spores with
special reference to Pilobolus . . . . . . . . .251
GENERAL SUMMARY
Part 1 261
Part II 268
EXPLANATION OF PLATES I.-V 270
PLATES I.-V To follow p. 274
GENERAL INDEX . 275
PART I
AN ACCOUNT OF THE PRODUCTION, LIBERATION, AND
DISPERSION OF THE SPORES OF HYMENOMYCETES
TREATED BOTANIC ALLY AND PHYSICALLY
INTRODUCTION
THE researches recorded in Part I. were undertaken with the object
of throwing light upon the production, liberation, and dispersion
of tjie spores of Hymenomycetes. More especially, an effort has
been made to find out how the spores manage to escape from the
hymenial surfaces where they have been produced, and how they
find their way between gills, down tubes, &c., to the exterior of the
fruit-bodies. By using appropriate optical methods, it has been
attempted to follow the spores individually from the moment they
leave the basidia, to determine their paths through the air, and to
measure by accurate means their rate of fall. This part of the
research has led me to the border-land where botany passes into
pure physics. Hitherto, it appears that physicists have never yet
determined directly by experiment the rate of fall of individual
microscopic spheres with a diameter of 3-10 /* through air. 1 There-
fore, by means of observations on the fall of spores, I have en-
deavoured to test the well-known and often assumed Stokes' Law.
In studying the effect of external conditions upon the liberation
of spores, and in determining the length of the spore-fall period,
the work has been much simplified by two discoveries. The first
is that spore-clouds, and even individual spores, can be seen falling
beneath a fruit-body without magnification when illuminated with
a concentrated beam of light. Whether or not spores are falling
from a fruit-body can thus be ascertained in a few seconds. The
second discovery is that practically all the leathery or corky fruit-
bodies to be found on logs, ie. those belonging to the genera Lenzites,
Polystictus, Dtedalea, Stereum, &c., retain their vitality on desicca-
tion for months or years, and that, when they are subsequently
placed under moist conditions, the liberation of spores begins once
1 Cf. the Appendix to Chap. XV.
4 INTRODUCTION
more within a few hours, and continues for days or weeks. It was
therefore possible for me to collect a stock of these fruit-bodies in
autumn, to revive them at will, and thus to study the liberation of
spores throughout winter and spring.
There seems to be but little literature dealing with the liberation
of spores of Hymenomycetes. Some observations of Brefeld, 1 given
in a footnote in his description of the life-history of Coprinus ster-
corarius, will be mentioned and criticised later on. Richard Falck -
has published a paper on the scattering of spores of Basidiomycetes,
in which he has given an account of the gradual accumulation of
spore-deposits on upper surfaces in closed chambers. He did not
succeed in actually seeing the spores in the air, but his experiments
showed that they are carried with remarkable ease by the slightest
air-currents. This fact can be verified directly and very simply by
means of my beam-of-light method, and rendered capable of mathe-
matical treatment by an exact determination of the rates of fall of
the spores in still air.
A visible spore-discharge from a fruit-body has been occasionally
observed as a very rare phenomenon by a few botanists. To the
records of Hoffman, H. von Schrenk, and Hammer 3 will be added
my own upon the visible discharge of spores from fruit-bodies of
Polyporus squamosus.
In his translation of Pfeffer's Physiology of Plants, Ewart 4 added
a brief statement of some of my then unpublished conclusions con-
cerning the liberation and fall of spores. The evidence in support
of these conclusions is brought forward for the first time in this
book.
In an account of the biology of Polyporus squamosus, I recorded
a number of observations upon the fall of spores in that species, and
gave an illustration showing the paths taken by the spores in falling
down the hymenial tubes. 5 A subsequent calculation, however,
Brefeld, Botanische Untersuchunyen iiber Schimmelpilze, III. Heft, pp. 65, 66.
R. Falck, "Die Sporenverbreitung bei den Basidiomyceten," Beitriige zur
Bio ogle der Pflanzen, Bd. IX., Heft 1, 1904.
For references, vide infra, Chap. VI.
Pfefter, Physiology of Plants, translated by A. J. Ewart, vol. iii. 1906, p. 416.
Buller, "The Biology of Polyporus squamosus, Huds., a Timber-destroying
Fungus," TJie Journal of Economic Biology, vol. i., 1906, p. 131.
INTRODUCTION 5
has taught me that the curves which we shall refer to later on as
sporabolas, should have been made to turn more sharply from the
horizontal to the vertical direction. This correction is given in
Fig. 66 (p. 189).
The material for the present investigation has included more
than fifty species, chiefly belonging to the Agaricinese and Polyporea3.
Species of Thelephorete and of Hydnese have been used less often.
The research has not been extended to the Clavariese, but there
seems to be no reason to expect that the mechanism for spore-
discharge in this group is different from that in those already
named. To what extent my generalisations upon the liberation of
spores into the air are applicable to the gelatinous fungi, only further
investigations can decide. Spore-discharge was found to take place
in the normal manner in Hirneola auricula-judte, but the mode of
spore-dispersion is not clear to me in gyrose Tremellinene. In the
light of my observations upon other fruit-bodies, it seems difficult
to understand how spores produced on a hymenium which looks
upwards can escape into the air. Possibly only those spores are
thus set free which are developed on that part of the hymenium
which is situated in a vertical or downwardly looking position.
Possibly the wind is not the only agent in the dispersion of the
spores. This matter certainly requires further elucidation. Un-
fortunately, gyrose Tremellinese so far have not been at my disposal.
The general result of the observations recorded in this book
seems to be that of laying emphasis on the fact that the fruit-bodies
of Hyinenomycetes are highly efficient organs for the production
and liberation of spores. In the case of the Coprini, I believe that
the old puzzle as to the significance of " deliquescence " has at last
been solved. It can be shown, e.g. in Coprinus comatus, that auto-
digestion takes place for the purpose of permitting the spores to be
liberated into the air, and is correlated with several other structural
and developmental features in the fruit-bodies in question. It has
become clear to me that, included in the Agaricineee, there are two
distinct fruit-body types for the production and liberation of spores
the Mushroom, or Psalliota type, and the Coprinus comatus type.
The latter appears to have been evolved from the former, and to be,
in some respects at least, superior to it in point of efficiency.
CHAPTER I
THE HYMENIUM BASIDIA AND PARAPHYSES NUCLEAR PHENO-
MENATHE COLOUR OF SPORES TWO-SPORED BASIDIA IN
CULTIVATED VARIETIES OF PSALL10TA CAMPESTRISOCCA-
SIONAL STERILITY OF COPRINUS FRUIT-BODIES CYSTIDIA
FUNGUS GNATS, SPRINGTAILS, AND MITES POSITION OF THE
HYMENIUM COMPARISON OF THE BASIDIUM WITH THE ASCUS
THE EFFECT OF SUNLIGHT UPON SPORES
THE hyinenium of most Hyinenomycetes is made up of spore-
bearing basidia and of sterile paraphyses. In a great many
species, it consists solely of these two kinds of elements ; but in
a number of others, cystidia and other specialised cells enter into
its structure.
Basidia and Paraphyses. It is a general rule, with compara-
tively few exceptions, that each basidium produces four sterigmata.
Each sterigma tapers conically, and bears at its apex a single spore
which, although sometimes spherical, in most cases is oval in shape
(Fig. 55, p. 162). The spore-wall in some species bears spines, but
usually is quite smooth. A sterigma, at the point of attachment to
its spore, has an extremely small diameter which in many instances
measures only 0-5 /* (Plate I., Fig. 34; Plate III., Fig. 16). This
narrow neck is of great importance, for, when a spore is set free,
the neck breaks across and the spore is projected with considerable
violence straight outwards from the basidium. 1 It must be at
the neck that the propelling force conies to be exerted.
The spores of all Hymenomycetes are very adhesive, and on con-
tact readily adhere to one another or to any object upon which they
settle. As if to prevent them touching one another during develop-
ment and discharge, the four spores on a basidium are borne
laterally on the sterigmata in such a manner that they are situated
as far apart as possible (Plate I., Fig. 3, a ; Plate III, Fig. 16).
1 Vide infra, Chap. XI.
BASIDIA AND PARAPHYSES 7
In the Coprini, the hymenium, when seen in face view, presents
to the eye a remarkably regular pattern (Plate III., Fig. 15).
The basidia, bearing black spores, are evenly spaced between the
paraphyses. Adjacent basidia, in a zone proceeding from below
upwards on each gill, ripen their spores simultaneously. Hence,
on any small portion of a gill, all the basidia are practically in
the same stage of development. It appears to be the chief
function of the paraphyses to act as spacing agents, so that by
their presence they prevent the spores belonging to adjacent
basidia from coming into contact. The large, unicellular cystidia
which are so prominent on the swollen edges of the gills in rnany
species, e.g. Coprinus conwtus, seem to be significant in that they
form suitable surfaces of contact where the gills touch one another
and the stipe. The swollen gill-margins serve to keep the gills
sufficiently separated from one another, during the development
of the basidia and spores (Plate I., Fig. 5; Plate III., Fig. 14).
If the gills were not kept apart, the spores of opposing gills would
touch one another, and, owing to their great adhesiveness, would
stick together. The proper spacing of the gills during develop-
ment, therefore, is essential in securing the efficiency of a fruit-
body as a spore-producing organ.
Excluding the highly specialised Coprini, we find that in the
Agaricinea3 generally, as well as in the other groups of Hymeno-
mycetes, the basidia do not all ripen on any part of the hymenium
simultaneously. Adjacent basidia on the gill of a Mushroom,
in the hymenial tube of Polyporus squamosus, &e., are at any
one time in the most diverse stages of development (Plate I.,
Fig. 3). A basidinm, bearing ripe spores, may thus have
adjacent to it one basidium which has shed its spores some
hours or days previously; a second which has spores in the most
rudimentary condition ; and, possibly, yet a third upon which not
even the sterigmata have appeared. Neighbouring basidia with
ripe spores are often very closely situated, but never near enough
to touch one another. To what extent this spacing is brought
about by the paraphyses, or by other basidia, is difficult to deter-
mine. Possibly, the fact that, in a Mushroom, adjacent basidia
ripen and shed their spores successively, instead of simultaneously,
RESEARCHES ON FUNGI
permits of the hymenium being constructed with less space devoted
FlG. 1. An Elm (Ulmus montana) with five fruit-bodies of Polymrus touanuuus
growing out from a large wound surface where a great branch had been broken
off. The uppermost fruit-body has a vertical central stipe in the middle of
AboS riaXS R H ' ?iCkard ^ * he Elind ylUm>
to sterile paraphyses in that species than is required for a Coprinus.
NUCLEAR PHENOMENA 9
The spacial arrangements of the basidia and their successive
development certainly require a more detailed study in the Mush-
room and fruit-bodies of the same type. 1
Nuclear Phenomena. The nuclear changes occurring in the
basidia and paraphyses during development have now been investi-
gated by modern methods, and it has been found that each hymenial
cell, when first formed, contains two nuclei. 2 In cells destined to
become basidia, the nuclei fuse to form a single nucleus. By means
of two successive bipartitions the fusion nucleus then divid.es into
four nuclei, whereupon the sterigmata and spores begin their
development. When the spores have attained a certain size, the
four nuclei severally and simultaneously approach the four sterig-
mata, creep through them, and pass into the spores, each of which
thus becomes provided with a single nucleus. Whilst making
their way into the spores, it is necessary for the nuclei to squeeze
through the very narrow sterigmatic necks, which feat is accom-
plished by their becoming compressed into slender filaments.
The extent to which the nuclei suffer constriction affords strik-
ing evidence of protoplasmic plasticity, and may be regarded as
indicating that cytoplasm may move with considerable ease
from cell to cell through pits in cell-walls. It seems to be
highly probable that a ripening spore becomes cut oft' from its
sterigma by a cell-wall, which eventually becomes double. If
this were not the case, one might expect that spore-discharge
would be accompanied by the collapse of both spores and basidia ;
but this I have observed does not occur. 3 However, anatomical
evidence of the existence of the double wall just before spore-
discharge has not as yet been obtained.
As the spores are ripening, the basidium is devoid of nuclei.
However, its cytoplasm remains living, and is useful in main-
1 The gills of Panseolus phalxnarum and of some allied species become finely
mottled at maturity. Numerous ripe spores are to be found on the darker areas,
whilst those on the lighter areas are still uncoloured.
- I have not made any original investigations upon the cytology of the de-
veloping hymenium. The facts here given in this connection are taken from
the paper by VV. Ruhland, " Zur Kenntniss der intracellularen Karyogamie bei den
Basidiomyceten," Bot, Zeit., 1901, Abt. I., pp. 187-204.
3 Vide infra, Chap. XTT.
io RESEARCHES ON FUNGI
taining the turgidity of the cell. The gill of a Coprinus comatus
was laid on a glass slide. On looking at one of the hymenial
surfaces from above with a microscope, I observed that, as the
gill began to lose water, the four sterigmata of each basidium
bent together so that the spores came into contact and adhered
to one another. The turgidity of the basidium is important
therefore in that it serves to keep the spores in their proper
positions in space. In dry weather, spores which have a
relatively high ratio of transpiring surface to volume lose water
rapidly, and a constant stream must flow to them through the
sterigmata in order to prevent them from collapsing. 1
In hymenial cells destined to remain sterile, i.e., to become
paraphyses, the two original nuclei with which each is provided,
do not unite with one another, but remain small and show no
signs of special activity. It is conceivable that at first all the
hymenial cells have equal possibilities of development, but that
for some reason the hymenium becomes divided up physiologically
into small areas, in each of which only a single cell can develop
into a basidium. We might suppose that each basidium has a
sphere of influence and by its own development causes the cells
adjacent to it to remain sterile. The problem of the spacial
arrangement of basidia upon a hymenium seems to be essentially of
the same nature as that of the arrangement of gills, hymenial tubes,
or spines on pilei, or as that of the arrangement of leaves upon stems.
The nature of the nuclear fusion in basidia is a matter which
is still under discussion. Dangeard 2 regards it as morphologically
and physiologically equivalent to a sexual act, and this view has
been accepted by Brefeld. 3 The union of the two nuclei called
karyogamy must lead to a doubling of the number of chromo-
somes. The reduction of the latter to one half the number
which we may suppose characterises the nuclei of the mycelium
and of the non-basidial cells of the hymenophore is in all
1 Cf. Chap. XVI.
2 Dangeard, " La sexualite chez les Champignons," Revue Scientifique, 5 e serie,
T. IV., 1905. Abstract in Bot. Centralb., Bd. GIL, 1906, p. 378.
3 O. Brefeld, Untersuchungen aus dem Gesamtgebiete der Mycologie, Bd. XIV.,
1908, pp. 246-256.
NUCLEAR PHENOMENA 11
probability brought about in the basidium itself during the two
successive bipartitions of the fusion nucleus. The two original
nuclei in each basidium are not sisters but are very remotely
related to one another. Investigation seems to show that they
are derived by a long series of successive conjugate divisions from
a pair of nuclei, the two members of which come to lie side by
side prior to the development of the fruit-body. The nucleus
which wanders into a spore soon divides into two after its entry
so that each spore becomes binucleate. 1 As soon as the- spore
germinates, these two nuclei enter the germ-tube, where they divide
at different rates and not in a conjugate manner. 2 By further
nuclear divisions the germ-tube comes to contain more than eight
nuclei in Hypholoma perplexum, and up to thirty in a species of
Coprinus. 3 However, so far it has not been found possible to
determine exactly where the first pair or first pairs of nuclei come
into existence. 4 In one group of Basidiomycetes the Uredinese
Blackrnan 5 and others 6 have observed that each pair of nuclei
which undergo fusion in the teleutospore, is derived by a long
series of successive conjugate divisions from a pair of nuclei brought
into existence by the conjugation of neighbouring mycelial cells.
The wall between the two cells becomes perforated and the nucleus
of one cell wanders into the other cell. It yet remains to be
decided whether or not anything of a similar nature occurs in
the Hymenomycetes. In this connection some interesting dis-
coveries may be in store for us. In species of Coprinus, &c., where
it has been found possible to obtain fruit-bodies from the mycelium
produced from a single spore, doubtless cross- fertilisation between
two individual mycelia either does not occur or is not necessary
for the completion of the life-cycle. Whether or not cross-
1 Miss S. P. Nichols, " The Nature and Origin of the Binucleated Cells in some
Basidiomycetes," Trans, of the Wisconsin Acad. of Sciences, Arts, and Letters, vol. xv.,
1904, pp. 30-70. Abstract in Bot. Zeit., Abt. II., Bd. LXIV., 1906, p. 266.
2 Ibid. 3 Ibid. * Ibid.
5 V. H. Blackman, "On the Fertilisation, Alternation of Generations, and
General Cytology of the Uredinese," Ann. of Bot., vol. xviii., 1904.
6 A. H. Christman, "Sexual Reproduction in the Rusts," Bot. Gas., vol. xxxix.,
1905; also E. W. Olive, "Sexual Cell Fusions and Vegetative Nuclear Divisions
in the Rusts," Ann. of Bot., vol. xxii., 1908.
12 RESEARCHES ON FUNGI
fertilisation ever occurs in any species of Hymenomycetes can
only be decided by extended observations. At present no Hymeno-
mycetes seem to be known which suggest that they are hybrids
produced from two individuals of distinct species. However, it
would be interesting to plant the spawn of several distinct varieties
of the cultivated Mushroom (Psalliota campestris) side by side in
beds of manure, and to observe whether or not under these con-
ditions any intermediate fruit-bodies would be produced.
It seems probable that the original sexual organs of Hymeno-
mycetes those corresponding to oogonia and antheridia in Asco-
mycetes have disappeared, and that a new form of sexuality has
arisen by the fusion in the basidia of the descendants of what
were originally merely vegetative nuclei. 1 This view is supported
by the discovery of Miss 'Fraser, 2 that in Humaria rutilans, one
of the Ascomycetes, normal fertilisation by means of sexual organs
is replaced by the fusion of vegetative nuclei in pairs a process
analogous to that which takes place in pseudapogamous fern pro-
thallia and also in the Uredineae.
The Colour of Spores. The colour of spores has long at-
tracted attention, owing to the fact that it has provided a useful
means of subdividing the Agaricineae. It must be admitted,
however, that the classification of this great group according
to spore colour is a purely artificial arrangement, although it
fulfils its primary object of enabling the student the more
readily to find the name of a particular species. There is no
good reason for believing that the Melanospone, the Porphyro-
spone, the Ochrosporse, the Rhodosporee, and the Leucospone are
separate and distinct offshoots from a common stock, and this has
been fully recognised by Hennings in his treatment of the Agari-
cineae in Die natilrlichen Pflanzenfamilien of Engler and Prantl.
- 1 The vegetative origin of the fusion nuclei in Hymenomycetes seems to be
generally accepted. Cf. N. Bernard, " Phenomenes reproducteurs chez les Cham-
pignons superieurs," Bull, mens Assoc. fr. Avanc. Sc., 1905. Abstract in Bot.
Centralb., Bd. CL, 1906, p. 394; Miss H. C. I. Fraser, "Nuclear Fusions and
Reductions in Ascomycetes," Brit. Assoc. Report for 1907, p. 688; also O. Brefeld,
1908, loc. ft*., p. 256.
2 Miss H. C. I. Fraser, "Contributions to the Cytology of Humaria rutilans,"
Ann. of Bot., vol. xxii., 1908, p. 42.
THE COLOUR OF SPORES 13
In a classification purely on the colour basis, we are obliged to place
together such diverse black-spored genera as Coprinus, Anthraco-
phyllurn, and Gomphidius. Coprinus is a highly specialised genus,
the fruit-bodies of which are fragile and often " deliquescent." On
the other hand, the fruit-bodies of Anthracophyllum are tough and
possess leathery or horny gills. 1 This genus is evidently much more
closely related to the white-spored Xerotus, Lentinus, and Marasmius
than to Coprinus. Gomphidius, with its fleshy fruit-bodies and
thick, fleshy, non-deliquescent gills, seems to be more closely
related to the white-spored Hygrophorus than to either Coprinus
or 'Anthracophyllum. This example will serve to show that
spore colour by itself is not a safe guide in deciding generic
relationships.
During the evolution of the Hymenomycetes there must have
been an evolution of spore colour, and it would certainly be very
interesting if some law of progressive colouration could be dis-
covered. It seems to me that a fairly good case has been made
out for the view that, in flowers in general, yellow is a more primi-
tive colour than red, and red more primitive than blue ; 2 but no
attempt to work out the phylogeny of the colour of spores has
yet been made. Massee came to the conclusion that the genus
Coprinus is the remnant of a primitive group from which have
descended the entire group of the Agaric inese, 3 and he then made
the deduction that since Coprinus spores are black, blackness in
spore colour is a primitive feature. According to this view, the
species of Agaricinese with yellow, red, brown, purple, and white
spores have descended from black-spored ancestors. In Chapter XIX.
I shall bring forward what I believe to be strong reasons for dis-
senting from Massee's view as to the ancestral position of the
Coprini. If, as I hold, the genus Coprinus has been derived from
fungi having radially symmetrical, stiped, non-deliquescent fruit-
bodies, with the Mushroom type of spore-liberation, then Massee's
1 P. Hennings in Engler u. Prantl, Die nut. Pflanzenfamilien, Teil I., Abt. 1**,
p. 222.
2 Grant Allen, The Colours of Floicers (Macmillan & Co.), 1891, pp. 17-60.
3 G. Massee, " A Kevision of the Genus Coprinus," Ann. of Bot., vol. x., 1906,
p. 129.
14 RESEARCHES ON FUNGI
theory of the primitiveness of blackness as a spore colour loses
its chief support.
On general grounds, I am inclined to regard colourlessness as
the most primitive condition in spores. We may well believe that
at first the conidia were as colourless as the basidia off which they
became constricted. It seems to me probable that the various
pigments were only gradually developed, possibly by a series of
mutations. Many so-called black spores are not truly black ; thus
in Gomphidius the spores are smoky-olive, and in Coprinus atra-
mentarius the spore powder has a brownish tinge. Intermediate
gradations of this kind seem to suggest that blackness in spores
was not acquired all at once but step by step. This view is further
supported by ontogeny. Thus in Coprinus comatus the spores
when very young are colourless; they then become pinkish, and
thereby turn the gills pink ; they then gradually become black.
In many species of Coprinus the spores whilst ripening become
brown, and the brown colour then gradually deepens into black.
As further support for the view that colourlessness in spores is a
primitive feature in Hymenomycetes, may be mentioned the fact
that five out of the six genera of Hypochnaceae, 1 as well as such
a primitive genus of Thelephoreae as Corticium, have unpigrnented
spores.
No suggestion has yet been made as to the significance of the
colours of spores. It is certain that some colouring matters, e.g.
those of heart-wood, of sclerenchymatous strands in the rhizomes
of ferns, of carrot roots, and of the rhizomorpha subterranea of
Annillarm mellea, cannot be of ecological value, since they are
developed in organs not normally exposed to the light. Possibly,
too, the colouring matters of spores are useless so far as their
colour properties are concerned : they may be merely bye-products
of certain metabolic processes. However, it will shortly be shown
that sunlight is injurious to the spores of certain Hymenomycetes.
It therefore seems possible that the various colouring matters
deposited in spore walls may be of value in that they serve to
absorb injurious rays of light, thus preventing them from reaching
the living protoplasm. If coloured spore walls are useful in filtering
1 P. Hennings, loc. Y., p. 114.
TWO-SPORED BASIDIA 15
sunlight, future experiments should show that the black spores of
Coprini and other Melanospone suffer less from prolonged exposure
to the sun than the colourless spores of the Leucosporse.
Two-spored Basidia in Cultivated Varieties of Psalliota cam-
pestris. Atkinson 1 has observed that the basidia of the cultivated
forms of Psalliota campestris (the varieties Columbia, Alaska, Bohemia,
and others) are two-spored, whereas those of the wild field form are
four-spored. However, he found a two-spored variety of Psalliota
campestris in the open once on a lawn, and once on the hillside of
a wooded ravine on the campus of Cornell University. My own
experience is similar to that of Atkinson. I have noticed that the
basidia of the wild form of Psalliota campestris obtained from fields
near Birmingham, England, are four-spored, and that those of a
cultivated variety on sale in Winnipeg are two-spored. I have also
observed a two-spored form occurring on manured ground included
within the campus of the University of Manitoba. The campus
Mushrooms differed considerably from the wild field Mushrooms of
England in that they were more scaly, browner, and possessed rela-
tively very shallow gills. Whether or not normal two-spored forms
of Psalliota campestris occur in nature as constant types still seems
to be a matter of doubt. Atkinson thinks it probable that the
cultivated varieties of Psalliota campestris originated as mutations
either from Psalliota campestris, or from some other species which
has been confounded with it ; and with this view I am inclined to
agree. Of two equally well developed Mushrooms, one of which
possessed four-spored and the other two-spored basidia, the former
would doubtless produce the greater number of spores, and therefore
be the more efficient reproductive organ. If this be granted, the
two-spored varieties of Psalliota campestris may be regarded as
degenerate mutations derived from four-spored ancestors.
Occasional Sterility of Coprinus Fruit-bodies. One of the
most curious phenomena which has come to my notice in
studying the Hymenomycetes, is the occasional sterility of
Coprinus fruit-bodies. Strange indeed is the reproductive organ
which otherwise undergoes normal development but fails in its
1 G. F. Atkinson, " The Development of Agaricus campestris" The Botanical
Gazette, vol. xlii., 1906, pp. 200-261.
1 6 RESEARCHES ON FUNGI
essential function of producing spores. Instances of sterility of this
kind have been noticed in two different species. A board was found
in a cellar infected with Coprinus fimetarius, var. cinereus, and a
small piece of it, bearing a young fruit-body, was sawn off, brought
to the laboratory, and placed in a damp-chamber. After further
development the fruit-body attained average size and form, but
exhibited the peculiarity of being yellowish-white in colour instead
of ashy grey. Upon examining the pileus with the microscope, I
found that it was almost completely sterile. Only a few basidia had
produced spores, whilst the great majority had remained in a rudi-
mentary condition. The normal basidia were found chiefly at the
pileus margin, but a very few were sparsely scattered over the
general surfaces of the gills. Two other fruit-bodies subsequently
appeared on the piece of board, but in these the spores were
developed in the usual manner. Coprinus plicatiloides l was grown
on sterilised horse-dung, from the surface of which its fruit-bodies
were produced in large numbers, several each day for more than a
month. At successive intervals about six fruit-bodies came up,
which seemed to be quite normal in size and form, but which were
conspicuous among their companions by being whitish-yellow instead
of grey. The microscope revealed the fact that the gills had failed
to produce any spores. The basidia, surrounded by large paraphyses,
had remained quite small ; they did not protrude beyond the general
surface of the hymenium and, so far as I could observe, they had not
even given rise to sterigmata.
The cause of the occasional sterility of Coprinus fruit-bodies seems
to be somewhat obscure. Since, however, the sterile fruit-bodies of
Coprinus plicatiloides grew in company with, and closely adjacent
to, other fruit-bodies which were completely fertile, it seems safe to
infer that the sterility was not conditioned by temperature, light,
heat, moisture, or atmospheric gases. Perhaps the phenomenon is
due to some accident happening to the mycelium at the time when
its contents are being poured into the young fruit-body. It is con-
ceivable that, if the mycelium attached to the fruit-body were
reduced in quantity, the fruit-body might suffer from starvation
during its further development, and yet, in consequence of the
1 For nomenclature of this species, vide infra, Chap. IV.
CYSTIDIA 17
continued absorption of water, still be able to stretch its stipe and
expand its pileus. The diminution in the supply of food materials
might lead to the non-development of the basidia. I have attempted
to induce sterility in Coprinus plicatiloides by mechanically dis-
turbing the substratum of young fruit-bodies, and have partially
succeeded. In one experiment a large fruit-body became pale
yellowish-grey at maturity, and it was found that the number of
basidia which had developed in the neighbourhood of the stipe was
very much below the normal. However, it must not be supposed
that sterile fruit-bodies are produced only after artificial disturbance
of tfre substratum," for in one instance, in a culture left undisturbed
for some weeks, two fruit-bodies of equal size came up side by side
with the bases of the stipes in contact, yet one of them was perfectly
fertile and the other quite sterile.
Cystidia. The significance of cystidia, once thought by Corda,
Hoffman, 1 Worthington Smith, 2 and others, to be male organs, still
seems not to have been elucidated with any certainty. According
to Cooke, 3 " The usual interpretation of the function of cystidia is,
that they are simply mechanical contrivances projecting from the
hymenium and thus keeping the gills or lamelbe apart." Possibly
this view may be correct for certain species of Coprinus, e.g.
C. micaceus, where large cystidia are found on the gill surfaces ; but
where cystidia coat the swollen gill edges, as in C. contains, we
may regard them as packing cells. They form cushions where
the gills are in contact with each other and the stipe, and they
probably facilitate the separation of these structures on the ex-
pansion of the pileus. Stress has already been laid on the necessity
for the provision of spaces between adjacent gills during develop-
ment, owing to the adhesiveness of the spores ; but these spaces
can be brought into existence, e.g. in C. comatus, by other
means than by the production of cystidia (vide infra, Chap. XIX. ;
Plate I. Fig. 5 ; Plate III. Fig. 14). In the genus Peniophora, thex
1 H. Hoffman, "Die Pollinaiien und Spermatien von Agaricus," Rot. Zeit.,
xiv., 1856, pp. 137-48, 153-63.
2 Worthington Smith, " Reproduction in Coprinus radiatus," Grevillea, vol. iv.,
1875-6, pp. 53-65.
3 M. C. Cooke, Introduction to the Study of Fungi, London, 1895, p. 41.
B
1 8 RESEARCHES ON FUNGI
cystidia (metuloids), which are very numerous, prominent, and
encrusted with calcium oxalate, could not possibly act as spacing
agents ; for here the hyrnenium is smooth. Possibly, in this genus,
they serve to protect the fruit-bodies from slugs or other harmful
animal parasites. The same interpretation might apply to the
rigid coloured setse of Hymenochtete, but does not seem suitable
for those of some species of the woody genus Fomes, e.g. F. nigricaws
and F. salicinvis.
De Bary's J investigation led him to the conclusion that in
Lactarius deliciosus the cystidia arise from ordinary hyphse of
the trama, but according to Massee 2 the cystidia of Russula and
Lactarius are direct terminations of the laticiferous system. Massee's
view is supported by the work of Biffen, 3 who found that in
Collybia velutipes the cystidia form the hymenial endings of the
conducting hyphse. In these cases, doubtless, the cell contents
are of importance, although exactly in what way still remains to
be explained. In Russula, at least, they do not seem to render
the gills unpalatable to slugs, since these animals are particularly
fond of the members of this genus, and often devastate the fruit-
bodies in a wood to such an extent that scarcely a single specimen
is left undamaged.
Earlier writers, Corda and others, stated that the cystidia of
the fleshy fungi discharge their contents through their apices in
the form of drops, but de Bary 4 and Brefeld could never satisfy
themselves that this is done spontaneously. However, Massee and
Worthington Smith have both upheld the older view. According
to Massee, 5 cystidia, when mature, contain glycogen which is emitted
through the nipple-like openings at their apices, and poured over the
surrounding hymenium, where it serves as food for the developing
spores. Smith 6 has figured the cystidia of Co^irinus atramentarius,
Gomphidius viscosus, and Agaricus radicatus as large, flask-like
1 De Bary, Comparative Morph. and Biol. of Fungi, English translation, 1887,
p. 304.
2 G. Massee, Journ. Roy. Micr. Soc., 1887, p. 205.
3 R, H. Biffen, Journ. Linn. Soc., vol. 34, 1898, p. 147.
4 De Bary, loc. cit. 5 G. Massee, loc. cit.
6 W. Smith, Grevillea, vol. x., 1881, p. 77 ; also Gardeners' Chronicle, Sept. 17,
1881, p. 367.
FUNGUS GNATS 19
structures with narrow necks each provided with a tiny operculum.
He states that the opercula drop off when the cystidia are mature,
and thus permit the cell-contents to escape. According to both
Smith and Massee, the cystidia in many cases drop out of the
hyineniuin after they have discharged their contents. A detailed
confirmation or refutation of these various statements seems to
me to be desirable.
In a recent paper Massee 1 has described two forms of cystidia
as occurring on the surface of the gills in the genus Inocybe the
ventricose and the fusoid. He states that the tip of each cystidiuru
becpines crowned "with mucilage, which escapes from the interior
after the deliquescence of the thin portion of the wall at its apex.
From the morphological point of view, we may follow de Bary
in placing cystidia in the category of hair formations. Since the
hymenial hairs are of several distinct types, it seems fairly certain
from analogy with the Phanerogams that they have different
functions varying with their structure. In some species they
may be only functional during the early development of the gills,
whilst in others they may be of importance afterwards.
From the point of view of spore-emission, cystidia have a limit
set to the distance they may project beyond the basidia. Where
a hymenial surface is in a vertical plane, they only project so
far that they do not interfere with the falling spores. These are
shot out horizontally from the basidia to a distance of about
O'l mm. They then make a sharp turn and fall down vertically
(cf. Fig. 64, p. 185, and Plate I., Fig. 4). Since the cystidia do
not project so far horizontally as the spores can be shot outwards,
they do not restrict the freedom of the latter whilst escaping from
the fruit- body.
Fungus Gnats, Springtails, and Mites. Possibly in some
instances cystidia may have become evolved in relationship with
insects or other small animals. Over one hundred and fifty
species of Mycetophilidje or " Fungus Gnats " have been described, 2
and most of them appear to live on fungi only. 3 The whole group
1 G. Massee, "A Monograph of the Genus Inocybe/' Ann. of Bot , vol. xviii.,
1904, p. 462.
2 Fred. V. Theobald, An Account of British Flies (Dipter.t), vol. i., 1892, p. 93.
3 Ibid., p. 96.
20 RESEARCHES ON FUNGI
is geologically of considerable antiquity, and specimens have often
been preserved very perfectly in amber. 1 At the present day, in
the genus Mycetophila, a female " lays her eggs generally on the
under surface of the pileus, walking about over the surface first
to find a suitable place, then depositing the ova singly." 2 The
eggs of the Mycetophilidae, after being laid, quickly hatch and
develop into the well-known maggots. These feed on the stipe,
the pileus flesh, or even the gills ; and they often cause the
infested parts to become rapidly and prematurely putrescent.
The gills of expanded fruit-bodies are frequently visited, not
only by Fungus Gnats, but also by Springtails (Collembola) and
Mites (Arachnida). As an instance, it may be mentioned that
on the under side of an unusually perfect fruit-body of Paxillus
involutus, which had just opened, I observed members of all
these three groups present in some numbers. So far as my
experience goes, it seems to be rather the rule than the exception,
that at least some small animals are to be found on all large
fruit-bodies. When a pileus is disturbed, the Springtails and
Mites run rapidly over the gill surfaces, but the Gnats usually
fly away. Some fruit-bodies of Polyporus squamosus, which were
growing on a log and had not yet become fully expanded, were
infested with small black Collembola. There were as many as
fifty to the square inch, and each one occupied a hymenial tube
which was just wide enough to hold it. The Springtails (genus
Achorutes), infesting the gills of Stropharia semiglobata and some
other species of Agaricinese, were found to contain spores in the
mid-gut. They are therefore parasites. It yet remains to be
investigated whether the hymenium, by means of its hairs, is
adapted in any way to suit its needs when visited by tiny animals ;
or whether, on the contrary, Mites and Springtails, &c., are simply
to be regarded as fungus fleas which have had no effect on the
phylogeny of their hosts.
1 Fossils have been found in the Upper Oolite beds in the South of England,
and also in the Solenhofen Slates. More than 280 species have been obtained
from the Tertiary in widely separated areas. Most of them were discovered in
the ambers of Europe and America, the rock specimens being few in comparison
(ibid, p. 93).
2 Fred. V. Theobald, An Account of British Flies (Diptera), vol. i., 1892, p. 94.
POSITION OF THE HYMENIUM 21
Position of the Hymenium. Excepting a few gelatinous species
which require further investigation, it is a general rule that in
Hymenomycetes the hynienium is situated on the underside of
the fruit-bodies. Encrusting forms, developing on logs and twigs,
usually produce their hymenium on the under or lateral surfaces of
the substratum'. 1 That the hymenium should not be developed on
a surface looking upwards is of great importance for spore-liberation.
It was found with the beam-of-light method that, if a fruit-body of
a Polyporus, Polystictus, Lenzites, Psalliota, Stereum, &c., is turned
OH its back, it is unable to liberate its spores into the air. It has
been determined that, if the hymenium on the gill of a Mush-
room, &c., is made to look directly upwards, the spores can be
shot upwards about 0*1 mm. above the basidia. 2 This does not
seem to be high enough to permit of the spores, which fall at the
rate of 1-5 mm. per second, being carried off by moderate air-
currents. Hence, when a hymenial surface looks upwards, the
spores shot upwards from it fall back again immediately on to
the hymenium and adhere there. Even when a fruit-body is set
in its natural position once more, such spores never regain their
freedom.
In the great groups of the Agaricinese and the PolyporeaB,
the fruit-bodies are characterised by having the greater part of
the hymenial surfaces disposed in almost vertical planes. In the
Agaricinese the hymenium is situated on the surfaces of wedge-
shaped gills (Figs. 2 and 3; also Plate I, Fig. 4); and in the
Polyporese it lines the inner sides of cylindrical or slightly conical,
vertically-placed tubes (Fig. 7, p. 33, and Fig. 66, p. 189). From
observations on the paths and rates of fall of individual spores, as
well as by direct beam-of-light studies of spore-clouds produced
from fruit-bodies when tilted at various angles, I have come to the
conclusion that it is only when the hymenium is vertical or looking
downwards at a greater or less angle that successful spore-liberation
1 I have noticed the fruit-bodies of Irpex obliquits growing on the upper side
of an inclined tree, but the hymenium appeared to be irregular. Falck (loc. ctY.)
grew abnormal fruit-bodies of Poria vaporaria and Merulius lacrimans on the upper
surfaces of wooden blocks in the laboratory.
Vide infra, Chap. XI.
22
RESEARCHES ON FUNGI
can take place in these groups. The mechanism for liberating
spores is of such a nature as to limit the possible forms of the fruit-
bodies in question.
Comparison of the Basidium with the ASCIIS. The vertical or
downwardly-looking position of the hymenial surfaces of Hymenomy-
cetes may be contrasted with
the upwardly-looking hymenial
surfaces of Discomycetes. From
the physiological point of view,
the ascus in this great group
of fungi is significant in that
it is an apparatus by which
spores may be liberated suc-
cessfully, when it looks upwards.
It is an explosive mechanism
of considerable efficiency. In
many instances it shoots out
its spores en masse to a distance
of one or several centimetres,
and thus causes them to be-
come effectively separated from
the ascocarp. 1 It seems to be
the development of the explosive
ascus which has permitted of the
fruit - bodies of Discomycetes
taking on their saucer- or
cup-like shapes. Here again,
as in the Hymenomycetes,
spore- liberating mechanism and
fruit -body structure go hand
FlG. 2. Group of young fruit-bodies of
Pleurotus ostreatnx (the Oyster Fungus)
growing from a wound on the trunk of
a Beech. The gills are developing in
vertical planes in response to a geo-
tropic stimulus. Photographed at
Sutton Park, Warwickshire, by J. E.
Titley. About natural size.
in hand.
There appears to be just as strict a correlation between the
general structure of an Agaricus or Polyporus and its basidia as
between the general structure of a Peziza and its asci. If the
basidia and asci in these types were interchanged, each fruit-body
would lose its efficiency. The spores could not be liberated, but
1 Vide infra, Part II.
BASIDIA AND ASCI
FlG. 3. Same group of fruit-bodies of Plcurotus ostrcatux as shown in Fig. 2,
photographed ten days later at maturity. The tops of the pilei have now
become flattened. The thin gills, separated by interlamellar spaces, have
developed along vertical planes, and are of various lengths, so as to be very
compactly arranged. The gills on the stipe of the lowest fruit-body have
been damaged by a slug. Photographed at Sutton Park, Warwickshire, by
J. E. Titley. About ^ natural size.
24 RESEARCHES ON FUNGI
would be entirely wasted. Not a single basidiospore would be shot
up far enough to succeed in escaping from a Peziza cup ; whilst in
a Mushroom or Polyporus the ascospores, when discharged, would
strike and adhere to the opposite hymenial surfaces. An upwardly-
looking, Peziza-like, cup-shaped Hymenomycete, provided with
typical basidia and liberating its spores into the air, is just as
impossible as a Mushroom- or Polyporus-shaped Ascomycete with
its hymenium composed of typical explosive asci. Where, in the
Hymenomycetes, as in the genus Cyphella, the fruit-body has the
form of a saucer, a cup, or a filter funnel, with the hymenium
inside, its mouth looks not upwards but downwards, so that it
resembles an inverted Peziza. It is true that the conical wine-
glass-shaped fruit-bodies of the species of the hymenornycetous
genus Craterellus stand erect. Here, however, in contradistinction
to Cyphella, the hymenium is borne on the exterior of the fruit-
bodies, whilst the interior is barren. The position of the basidia of
a Craterellus is exactly the reverse of that of the asci in the
erect wine-glass-shaped fruit-bodies of certain Ascomycetes. These
remarks may serve to emphasise the close correlation between the
mechanism for spore-liberation and fruit-body structure.
The Effect of Sunlight upon Spores. Some years ago, Massee l
expressed the view that the hymenium of the Hymenomycetes,
during progressive phylogenetic development, had come to be
placed on the lower sides of the pilei, instead of on the upper,
for the purpose of concealing it from the light. On the other
hand, my own researches seem to show that the position of the
hymenium has been primarily decided by the necessity of the
basidia being so placed that they can readily liberate their spores
into the air. Other, but subsidiary, advantages accruing to the
hymenium from its position on the lower side of a pileus, rather
than the upper, are: protection from rain, falling leaves, &c., and
undue transpiration in dry weather.
The exact efl'eot of direct sunlight upon the spores of Hymeno-
mycetes still remains to be worked out. In the Clavanea3, many
species live in fields, &c., where their hymenial surfaces are freely
1 G. Massae, " A Monograph of B.-itish Gastromycetes," Ann. of Bot., vol. iv.
1889, p. 2.
THE EFFECT OF SUNLIGHT UPON SPORES 25
exposed to the sun. During their transportation by the wind,
spores must often be exposed to sunlight for several hours together ;
by analogy, therefore, one might expect them to be fairly resistant
to its influence. However, an experiment by Miss Ferguson 1 tends
to show that light has an inhibitory effect on the germination of
the spores Psalliota campestris.
In order to test the effect of sunlight upon the vitality of the
spores of Schizophyllum commune, which are colourless, I proceeded
as follows. A fruit-body was revived in the manner to be described
in Chapter IX., and, when shedding spores, it was set in a closed
chamber (cf. Fig. 37, p. 97), at the bottom of which were two glass
slides lying side by side. In the course of a night the slides became
thinly and evenly coated with a spore-deposit, and next morning
they were removed from the chamber. One of them was then
supported by a clamp-stand so that it was freely exposed to the
direct action of the sunlight streaming through a window in the
laboratory, and the other was kept in the dark. The temperature
of the laboratory was about 19 C. Tests for germination were made
by placing the spores in hanging drops of a neutralised nutrient
medium consisting of 1 per cent, glucose, 1 per cent, peptone,
0-3 per cent, meat extract, 0-5 per cent, sodium chloride, and 10 per
cent, gelatine. The ring chambers containing the drops were
partially filled with distilled water, and were kept in the dark.
Comparative tests made during the month of April showed that
spores which had been exposed to sunlight for eight hours germi-
nated more slowly than spores which had been exposed to sunlight
for two hours, and these more slowly than those which had been kept
in the dark. Spores kept in the dark germinated about twenty
hours sooner than those which had been exposed to sunlight for
seven or eight hours. After three days the mycelia produced from
spores which had been kept in the dark were much more advanced
than those which had been produced from spores which had been
exposed to sunlight for periods of one, two, three, six, seven, and
eight hours respectively. It was also found that exposure of the
1 Miss M. C. Ferguson, " A Preliminary Study of the Germination of the
Spores of Agaricus campestris and other Basidiomycetous Fungi," C7.S. Dep. of
Agric., Bureau of Plant Industry, Bull. No. 16, 1902, p. 21.
26 RESEARCHES ON FUNGI
spore-deposits to sunlight resulted in a marked diminution in the
proportion of germinating spores. This series of experiments,
together with three others, has led me to the conclusion that, when
dried spores of Schizophyllum commune are exposed to direct
sunlight for a few hours, a certain proportion of them are rendered
incapable of germination, whilst those which germinate do so more
slowly than dried spores kept in darkness. Subsequent experiments
showed that the spores of Dxdalea unicolor are affected by sunlight
in the same manner as those of Schizophyllum commune. From
the point of view of spore-dispersion, the experiments seem to
indicate that the spores of these fungi, when drifting about in the
air, may survive exposure to sunlight for a whole day, and
that they may subsequently germinate, although with diminished
vitality. 1
1 The injurious effect of sunlight upon the development of pathogenic bacteria
is now well known. In the case of fungi, Elving has shown that the spores of
Aspergillus ylaucus, and Laurent that those of Ustilago carbo, are killed by long
exposure to sunlight. Pfeffer's Physiology of Plants, English translation, vol. ii.
p. 247.
NOTE. Since this chapter was set up, W. B. Grove has called my attention
to the fact that he has recorded (The Flora of Warwickshire, Fungi, 1891,
p. 419) the occurrence of a fruit-body of Stropharia semiylobata with the gills
white owing to the non-development of the spores, but otherwise perfect.
CHAPTER II
THE EXTENT OF THE HYMENIUM PRINCIPLES UNDERLYING THE
ARRANGEMENT OF GILLS AND HYMENIAL TUBES THE MARGIN
OF SAFETY THE GENUS FOMES
THE Hymenomycetes are classified in subdivisions corresponding
in the main with the manner in which the pileus is arranged in
relation to the hymenial surfaces. Only in the Thelephorea?, some
Tremelh'nea?, and the Exobasidiinese is the hymeniuui smooth and
flat, whilst in the Agaricinere it is arranged upon gills, in the
Polyporere in tubes, in the Hydne3 upon spinous prolongations,
and in the Clavariese upon the exterior of more or less numerous
branches of the fruit-body.
The various forms of fruit-bodies may be explained in their
evolutionary aspect on the supposition that a chief factor in their
survival has been the advantage arising from the production of
a relatively large number of spores with a relatively small expendi-
ture of fruit-body material and energy. The gills, spines, tubes, &c.,
all have the same significance, namely, that of increasing the extent
of the hymenium which a fruit-body may bear. The same end has
been attained by different means. One can easily imagine how,
beginning with the Thelephorese with smooth and flat hymenial
surfaces, the more highly complex fruit-bodies of the Agaricinea^,
the Polyporese, the Hydnere, and the Clavariese have been evolved.
The principle of folding to increase surface is well illustrated in
these four groups. Perhaps every possible means of economically
increasing hymenial surface, consistent with the liberation of the
spores, has been exhausted by them.
In order to obtain more precise information with regard to the
advantage obtained by the production of gills, spines, tubes, &c., a
number of calculations have been made.
Let A be the area of the flat surface on the underside of a
28 RESEARCHES ON FUNGI
fruit-body, when gills, tubes, or spines have been removed. Let
FlG. 4. Fruit-body of Polyporm squamosus nearly full-grown ; upper surface covered
with brown scales. The full length of the stipe is photographed. Photographed
by R. H. Pickard. natural size.
H be the area of the hymenium upon the gills, tubes, or spines.
TT
Then the ratio gives the increase of surface of the hymenium
THE EXTENT OF THE HYMENIUM 29
for which the gills, tubes, or spines are responsible. Let the
FIG. 5. Under surface of fruit-body of Polyportts sffuanioxus nearly full-grown,
showing the pores of the hymenial tubes and the reticulations on the stipe. The
fruit-body was photographed immediately after it was cut : the involution of the
edge of the pileus is quite natural. Photographed bv R. H. Pickard. ^ natural
size.
specific increase of hymenial surface, due to the presence of gills,
3 o RESEARCHES ON FUNGI
tubes, or spines in any fruit-body, be represented by the con-
traction Sp. Inc.
Then
Sp. Inc. = ~.
The value of the specific increase has been measured in a few instances.
For species of Agaricine;e the number of gills was counted and
the gill-systems studied. The number of gills of each size was
determined. A few gills of each size were dissected off the fruit-
body, placed on paper, and drawn. The paper drawings were then
cut out with scissors, and their area determined by weighing them
against squares of paper marked out in square millimetres. The
fact that each gill has two sides was taken into account. With the
data thus obtained the total area of the gills could be calculated.
The value of A was calculated from measurements of the diameters
of the pileus and of the stipe.
Full-grown specimens yielded the following results :
Species.
Diameter of
Pileus in
Millimetres.
Specific I lie-reuse of
Hymenial Surface
due to the Production
ol Gills.
Russula citrina .
63
7-0
Amanita rubescens .
50
10-0
>i ...
76
12-2
Armillaria mellea . .
76
12-8
Tricholoma personatum
127
16-0
Hypholoma sublateritium .
76
17-5
Psalliota campestris .
98
20-04
As an illustration of the method of calculating specific increase,
details for the specimen of Tricliolomci persona turn, will be given.
Diameter of pileus = 127 mm.
Diameter of stipe = 28
Hence, the area of the underside of the pileus, with the gills
removed, exclusive of the part occupied by the stipe, = 12672'S
-616 mm. 2 , or A =120-1 cm. 2 .
Number of primary gills = 101
secondary = 101
tertiary = 202
,, quaternary ,, = 404 approximately.
THE EXTENT OF THE HYMENIUM 31
By the weighing method already described, the area of the gills,
including both sides, i.e. H, was determined to be 1942 cm. 2
approximately.
Hence, Sp. Inc. = ~ = 16 approximately,
i.e. the fruit-body had sixteen times more hymenial surface than
it would have had if the underside of the pileus had not been
produced into gills.
In the case of the Mushroom, the gills on one quarter of
the ^pileus were isolated one by one, and their outlines marked
out on paper. The figures were then cut out and weighed
against paper ruled into square millimetres. The area so deter-
mined was multiplied by four, and thus the whole surface area
of the gills obtained.
From the above table it will be seen that the common field
Mushroom has the highest specific increase, namely 20. This is
not surprising, for field Mushrooms have deep gills closely packed
together (cf. Plate IV., Fig. 25). Russida citrina, on the other
hand, has much shallower gills of one length only, which are placed
at some distance apart. The specific increase in this species is
consequently very small : it is only 7, i.e. one-third of that of the
Mushroom. Again, it is clear that with pilei of equal diameters.
Hypholoma sublateritium has considerably more gill-surface than
either Amanita rubescens or Armillaria mellea. If we take the
specific increase of gill-surface as a test, it seeins fair to conclude
that of the fungi investigated, the greatest morphological advance-
ment is exhibited by Psalliota campestris and Hypholoma sub-
lateritium, and the least by Russula citrina.
In the Polyporete the formation of hymenial tubes often
leads to a considerable increase in the spore-bearing area.
The amount of increase depends upon the length and breadth
of the tubes. In three species the specific increase has been
measured.
Polyporus squamosus (Figs. 1 and 4-7). In the specimen
examined it was found that in the middle of the pileus there were
22 tubes to each square centimetre. Each tube on the average
32 RESEARCHES ON FUNGI
was 9 mm. long, and possessed a perimeter at its base of 6 mm.
Hence, the area of hymenium for each square centimetre = 9 x 6 x '22
= 1188 mm. 2 approximately. Therefore, for 1 cm. 2 , =100 mm. 2 ,
I -I Q Q
we find that the specific increase = = 11*8 approximately.
In most specimens of the fungus the tubes do not attain a length
of 9 mm. The specific increase is therefore usually less than 11-8.
By comparison with the results in the table given above, it may be
concluded that many Agaricineaj have a larger specific increase than
Polyporus squamosus. However, this species has unusually wide
tubes. When the tubes are very narrow, as in the cases of Fomes
vegetus and F. igniarius, now to be discussed, it is found that
FIG. fi. View of part of the underside of a mature fruit-body of Polyporus tquamonus
which was 2 ft. 2 in. across. The openings of the hy menial tubes are polygonal.
the specific increase may be much greater than that in any of the
gilled fungi.
Fomes vegetus. The fruit-bodies are perennial and produce
a layer of tubes annually (Fig. 11). In the specimen examined it
was found that for one year there were 2080 tubes to 1 square cm.
The length of each tube on the average was 12 mm. and the
diameter 0-17 mm. Hence, the area of the hymenium for each
square centimetre = 12 (^ x 0-17 jx 2080 = 14830-4 mm. 2 approx.
Therefore, for 1 cm. 2 , = 100 mm. 2 , we find that the specific increase
= 148 approximately. In the specimen examined three
THE EXTENT OF THE HYMENIUM
33
layers of tubes had been produced, and these possessed a total
vertical length of 40 min. Hence, taking the three years together,
the total specific increase amounted to 493.
Fomes igniarius. In this species also, the fruit-bodies are per-
ennial and produce successive layers of tubes. In a large specimen
it was found for one layer that in 1 sq. cm. the number of tubes
was 2000. The breadth of each tube on the average was O'lo mm.
and the length 4 mm. Hence, the area of hymeniuin for each
square centimetre = 4 ( x 0-15^ x 2000 = 3800 mm. 2 approximately.
OQrjTi
Therefore, for 1 cm. 2 , =100 mm. 2 , the specific increase = ^ = 38
approximately. In the specimen examined there were twenty-five
FIG. 7. View of part of a transverse section through the middle of a mature
fruit-body of Polyporus squamotus. The hymenial tubes are directed down-
wards. Natural size.
layers of tubes, having a total thickness of 100 mm. For the total
period of growth, therefore, the specific increase amounted to the
high value of 942.
From the figures just given, which show that in one year's
growth the specific increase for a specimen of Fomes ignarius was
approximately 38, and for one of F. vegetus approximately 148,
it is clear that the perennial Polyporeae with narrow tubes produce
much more hymenial surface for a given area of pileus than any of
the Agaricinea3. The specific increase for Psalliota campestris, which
was the highest in the Agaricineoe investigated, was only 20*04.
34 RESEARCHES ON FUNGI
We have seen that in the Agaricineae the extent of the
hymenium has been increased by the production of radial wedge-
shaped gills with vertical median planes, so that the fruit-bodies
are characterised by an admirable compactness. However, certain
principles underlying the spacing of the gills in reference to one
another still require an elucidation. The gills are usually crowded
together on the underside of a pileus. Two adjacent gills, how-
ever, must be a certain distance apart in order to permit of the
liberation of the spores. It will subsequently be shown 1 that for
Psalliota campestris, &c., the spores are actually shot horizontally
for about 0-1 mm. into the interlamellar spaces before their paths
of movement become vertical. Two adjacent gills, where they are
closest to one another, i.e. near the pileus flesh, must therefore be
separated from one another by a distance which at least just
exceeds Ol mm. In the Mushroom the minimum space between
the gills was actually found to be about 0-2 mm. (Plate I., Fig. 4).
Probably nearly 50 per cent, of this should be regarded as a
margin of safety. When a mature pileus is tilted slightly, so that
the plane of the flesh is no longer horizontal, the gills, displaced
from their vertical planes, react to the stimulus of gravity by
growth in such a manner that they quickly come to take up
vertical positions once more. 2 This, however, entails a reduction
in the margin of safety, for the spaces between the gills become
narrowed. If the pileus is tilted beyond a certain amount, it neces-
sarily follows that, when the gills have adjusted themselves, the
margin of safety must have disappeared altogether. This must lead
to a diminution in the number of spores escaping from the pileus.
In the Mushroom, judging from a study of gill-dimensions as
embodied in Plate I., Fig. 4, the margin of safety would not be
used up until the pileus had been tilted to an angle of about 30.
In this instance, and probably quite generally for Agaricinese, pro-
vided only that the gills have taken up vertical planes, just as
many spores can be liberated from a slightly tilted as from an
1 Vide infra, Chap. XI.
* Cf. A. H. R. Buller, " The Reactions of the Fruit-bodies of Lentinus lepideus,
Fr., to External Stimuli," Ann. of Bot., vol. xix., 1905, p. 432. Also vide infra,
Chap. IV.
THE ARRANGEMENT OF GILLS 35
untilted pileus. This arrangement must be
of some value, for in woods and fields slightly
tilted pilei with vertical gills are quite com-
monly met with. \ /
It is now clear that two adjacent gills *>
must be at least a certain minimum distance
apart to permit of the successful liberation
of the spores. It is equally clear, however,
that when the space between two gills ex- r 1 ^
ceeds a certain maximum their arrange- V *
merit is a wasteful one, for the underside
of the pileus is then not being used up to
the best advantage. The gills of Agaricineae
are disposed radially, so that in passing from
the stipe to the edge of the pileus they
necessarily diverge. Near the stipe two
adjacent gills may be economically spaced.
Further from the stipe, however, owing to
divergence, their spacing becomes wasteful.
There is much more room left between them
than is necessary for the liberation of the
spores, and for the provision of an adequate
margin of safety. This defect is obviated
almost entirely in most Agaricinese by the
introduction of shorter gills between the
longer ones, in succession, proceeding from
the stipe to the pileus periphery (Fig. 8).
In some specimens of Marasmius oreades
it was found that the gills were of three
different lengths, and that in a specimen
of Tricholoma personatum they were of four
different lengths. The complexity of the
gill-system is usually greatest in pilei with
large diameters. Good examples of the
economical arrangement of gills, so that
the space between any adjacent two shall Flo . 8 ._ As( ,,,,,of,iii s removed
never exceed a certain maximum width, SaShrSSi $Soio* *$?
<rw). Natural size.
36 RESEARCHES ON FUNGI
and yet never be less than a certain minimum width, are seen
in the Oyster Fungus (Pleurotus ostreatus, Figs. 2 and 3) and
in the Mushroom (Fig. 9 and Plate IV., Fig. 25). Certain species
of Russula have gills which are all of one length, with the
exception of very occasional shorter ones (Fig. 10). Since the
gills in the fully-expanded fruit-bodies diverge considerably in
FlG. 9. Psalliota campestris. Part of FlG. 10. The pileus of Russula nigricans
a pileus photographed from below, an Agaric iu which the gills are very
showing that the gills are accu- coarsely spaced. The stipe is maggot-
rately adjusted so that they look eaten. Reduced to natural size,
directly downwards. Natural size.
passing from the stipe to the margin of the pileus, their arrange-
ment appears to be relatively imperfect.
The principles underlying the arrangement of the gills of the
Agaricinese doubtless also apply to the arrangement of the hymenial
tubes beneath the pilei of species of Polyporese. Other things
being equal, the greatest economy is effected when the tubes are
THE GENUS FOMES 37
as numerous as possible, for this entails a corresponding increase
of hymenial surface. The diameter of the tubes, however, must
always be sufficiently wide to permit of the liberation of the spores.
Since these are shot outwards horizontally into the tubes for a
distance of about O'l mm., 1 the tubes can never be less than this
in diameter. In species of Polystictus and Foines, where the width
of the tubes is about 0-2-0-25 mm., the ultimate reduction con-
sistent with safety seems to have been attained.
The genus Fomes, from the point of view of efficiency in the
production and liberation of spores, may be looked upon 'as having
fruit-bodies of a highly specialised kind. In the first place the fruit-
bodies are perennial. This is economical, for the old flesh is used
FlG. 11. Fomes applanatus (~F. veyetus). Vertical section through a fruit-body
three years old. A new layer of hymenial tubes was produced each year.
Reduced to natural size.
each year to support new hymenial tubes, and does not function
only once, as in the case of such annual fruit-bodies as Polyporus
squamosus, or those of the Agaricinese, the Hydnese, the Clavariete,
or the Tremellineoe. Again, most of the Fomes fruit-bodies are very
hard and " woody," possess no stipes, and are attached by a broad
surface to the wood on which they are produced (Fig. 11). This
gives them extreme rigidity, so that even in the course of years
accidents are little likely to injure them. The extreme rigidity also
1 Vide infra, Chap. XI.
67838
3 8 RESEARCHES ON FUNGI
ensures that the very narrow hyinenial tubes shall be kept exactly
in the vertical position. The importance of this is obvious when it
is realised that even a very slight tilt of the tubes would prevent the
spores from escaping from them. 1 Further, the fruit-bodies can
withstand uninjured the severest frosts of winter, and, judging from
some experiments made with Fomes igniarius, can recover after pro-
longed desiccation. 2 Lastly, they have extremely narrow hy menial
tubes. This, as we have seen, involves a great increase of spore-
bearing surface. Taking into account the manner in which the
spores are discharged from the basidia in Polyporese (Fig. 66, p. 189),
it would seem that for F. vegetus and F. igniarius the width of the
tubes is so small that, after allowing for a small margin of safety,
it has almost, if not quite, reached its- limit.
The more liable a polyporaceous fruit-body is to become slightly
tilted, owing to developmental changes, transpiration, the accumula-
tion of rain-water on its upper surface, the visits of birds, &c., the
greater is the advantage of wide hymenial tubes over narrow ones in
liberating the spores. Perhaps it is for this reason that the tubes in
the soft and wide-spreading brackets of Polyporus squamosus are of
considerable width, so that they stand in marked contrast with those
of the more compact and extremely rigid fruit-bodies of Fovies
igniarius, &c. The dimensions of the tubes in these and other
species seem to me, at least to a certain degree, to be correlated with
the nature of the pileus flesh.
1 With the beam-of-light method (vide infra, Chap. VII.) it was observed that
when the tubes of Polystictus hirsutus were tilted to an angle of 15 from the
vertical, there was a marked diminution in the number of spores liberated, and
that with a tilt of 30 spore-liberation almost entirely ceased.
2 Specimens which had been gathered and kept dry for six months began to
grow on their undersides when they were placed in a damp-chamber.
CHAPTER III
THE FUNCTIONS OF THE STIPE AND OF THE PILEUS FLESH
THE GILL-CHAMBER
THE mechanics of the stipes of the more complex Hymenomycetes
might well form the subject of an interesting and a detailed investi-
gation. A few remarks may here be made in this connection upon
the stipes which are centrally situated beneath radiate pilei in the
most highly developed fruit-bodies. The stipe can support the
pileus with far less strain in a centric than in an eccentric position,
and it seems probable that this mechanical principle has been one of
the chief factors in bringing about the evolution of the umbrella
form of Agaric. In different species stipes vary much in length,
thickness, and in the nature and disposition of the materials of which
they are composed ; but no doubt there is always a correlation, and
often a close one, between their structure and the work which they
have to do in supporting the pileus at a distance from the ground,
and in keeping the gills in exactly vertical planes.
When one realises how very important it is, from the point of
view of spore-liberation, that the planes of gills, the axes of hymenial
tubes, &c., should be kept quite motionless in a vertical position, one
cannot be surprised to find that the mechanical structure of the
stipe and pileus flesh is such as to give the whole fruit-body a
remarkable amount of stability. Were the gills of Agaricineae, or
the hymenial tubes of Polyporea?, subjected to even slight continuous
tilting movements, it is certain that a great proportion of the spores
could never be liberated for after discharge from their basidia, vast
numbers of them would strike and adhere to the hymenium. In the
Mushroom, for example, it has been found 1 that in still air the paths
of fall of the spores in the interlamellar spaces are as shown in
Fig. 12, A. When the planes of the gills are tilted 1 30', the spores
1 Vide infra, Chap. XVII.
4 o
RESEARCHES ON FUNGI
can readily escape (B). If the tilt be increased to 2 30', the critical
angle is reached (C) : all the spores can still make their way out
between the gills, but with any increase in the tilt some of them fall
upon the hymenium and adhere there. With a tilt of 5 half the
spores are lost (D), and with a tilt of 9 30' four-fifths of them (E).
The gills of a Mushroom are radially disposed, and it is therefore
evident that, if a Mushroom is tilted, those gills with their planes
FlG. 12. The effect of tilting the gills of Psalllota campeslris. Two gills are shown
in cross section. The arrows in the interlamellar space indicate the paths of
the spores discharged in still air. A, gills in the normal position. In B the
gills are tilted 1 30' from the vertical, in C 2 30', in D 5, and in E 9 20'.
most nearly perpendicular to the plane of tilt will suffer most, whilst
those with their planes most nearly parallel to the plane of tilt will
suffer least. The exact proportion of spores lost by a whole Mush-
room with a tilt of a given angle would be somewhat difficult to
calculate, and no attempt will be made here to solve this problem.
It is sufficiently clear, however, that when the pileus of one of the
Agaricinese is tilted only a few degrees from its normal position, its
spore-liberating efficiency is greatly reduced. In this connection, it
is a distinctly significant fact that all hyrnenomycetous fruit-bodies
THE FUNCTIONS OF THE STIPE 41
are so constructed that in ordinary weather they remain quite
motionless. Those with the longest stipes, e.g. Coprinus comatus,
scarcely sway on very windy days, whilst most fruit-bodies remain
practically unstirred even during gales. In a field, the stability of a
Mushroom may be contrasted with the instability of a neighbouring
grass stein; but we must recognise that the peculiar mechanical
properties of both Cryptogam and Phanerogam are equally fraught
with a beautiful significance. Each plant reacts to the motion of
the breeze in a manner most suited to its own special needs.
Centric stipes are usually cylindrical. In some spebies, e.g.
Russulae, &c., the cylinder is quite solid, although, as a rule, it is
firmest toward the exterior ; in others, it has a narrow central core,
stuffed with soft, loosely interlacing hyphse, or left quite unfilled as
in Amanita phalloides (Fig. 13) or the Mushroom; whilst in yet
others, of which Coprinus coinatus is a good example, it assumes
the form of a perfect hollow cylinder with a comparatively thin wall
(Plate I., Fig. 1). The hollow cylinder has the same significance in
Fungi, in Flowering Plants, and in structures built by engineers.
Where it is employed, advantage is taken of the fact that with a
given length and a given amount of material, a hollow cylinder is
more rigid and offers more resistance to bending than a solid
one.
Where the pileus is large, as in many Russulse and Boleti, the
stipe is usually thick, solid, and so rigid or tough that it is not easily
displaced ; it appears to be constructed as if to resist more particu-
larly any downward pressure from above, arising from obstacles met
with in pushing up the broad pileus, or which might come to rest
on the fruit-body after its development. On the other hand, there
are many species with small pilei placed on long stipes. Here the
pileus is usually conical or dome-shaped, and the stipe forms a
perfectly hollow cylinder or one with a thin firm wall and a very
soft core. The whole fruit-body, whilst being fairly rigid, is much
more elastic than the larger ones to which we have referred, and
seems adapted for pushing its way up between surrounding grass
stems, &c., for throwing off rain-water, and for resisting lateral
pressure. Illustrations of long, hollow stipes may be found in the
genera : Mycena, Galera, Stropharia, Coprinus, &c. Thin-stiped fruit-
42 RESEARCHES ON FUNGI
bodies, e.g. those of Mycena epipterygia, have a distinct advantage
over thick-stiped, such as those of Russula emetica, in that, if the
fruit-body should be even considerably displaced by any accident,
it can quickly be set once more with the gills in vertical planes by
means of a suitable geotropic curvature of the stipe. With Russuhe,
Psalliotse, &c., owing to the thickness of the stipes, this is impossible
when the pilei have become outstretched. In these cases, the gills
themselves react to the stimulus of gravity, and after a slight dis-
placement of the fruit-body, quickly readjust themselves so as to
come to lie in vertical planes once more ; but when the displacement
is considerable, this remedy becomes of very little avail. In species
of Galera, Mycena, &c., the structure of the stipe is such as to remind
one of the hollow peduncle which supports the capitulum of a
Dandelion or the pith-filled one of a Chrysanthemum. It is clear
that for the stipes of Agaricineae we have a series of variations
in the cylindrical form comparable with that found in the stems of
Phanerogams and bearing a similar interpretation.
A certain amount of rigidity is given to many stipes, not merely
by their cylindrical form, but also by longitudinal tensions set up
in the layers of hyphse of which they are composed. The existence
of these tensions can easily be proved by partially bisecting or
quadrisecting the stipes concerned, e.g. those of Coprinus comatus,
Mycense, &c., in a longitudinal direction from below upwards, with
a knife. The halves or quarters so produced bend outwards and
resist attempts to replace them in their original positions (Fig. 13).
It is well known that similar tensions occur in the young stems
of the Higher Plants.
The foregoing remarks tend to show that stipes in general are
well adapted to give the basidia the best possible chance of dis-
charging their spores, so that they may freely escape from the
fruit-body. There can be no doubt that the pileus flesh is adapted
to the same end. Its function is not merely to support the weight
of the gills or hy menial tubes, but to hold them fixed in one
particular position. As one might expect from a very simple
mechanical consideration, the pileus flesh is always thickest toward
the centre and thins out rapidly in the peripheral direction. Its
exact form and the materials of which it is composed vary much
THE FUNCTIONS OF THE STIPE
43
in different species, so that its peculiar mechanical needs are
doubtless met in slightly different ways.
In certain species of Polyporus which have central stipes
P. pisochapani, P. rugosus, P. lepideus, and P. floccopus there
is present, according to Massee, 1 a highly developed mechanical
sheath to both pileus and stipe. The occurrence of this structure
points to an unusually marked division of labour between the
nutritive and supporting parts of the fruit-bodies.
In Coprinus coinatus (Plate I., Fig. 1) the pileus has the form of
a bell, and its centre
C
of gravity is situated
at soine distance be-
low its place of at-
tachment to the stipe.
It is thus in a state
of stable equilibrium,
and doubtless, in cor-
relation with this
mechanical fact, it
happens that the pi-
leus and stipe are very
loosely attached to-
gether. If one slightly
tilts the stipe of a
fruit-body which has
just opened, the pi-
leus refuses to become
FIG. 13. Amanita phalloides (volva removed). A, young
fruit-body. B, mature fruit-body. The stipe has
been quadrisected and the tensions in it have caused
the four parts to separate. C, cross-section of a stipe.
All | natural size.
tilted too, but instead remains in its optimum position. High
winds sometimes cause the pileus to swing slightly about the fixed
stipe. However, few or possibly none of the spores would thereby
be prevented from escaping from the fruit-body, owing to the
peculiar manner in which they are liberated. 2
Among the most beautiful Agarics in nature are the so-called
Parasol or Umbrella Fungi Lepiota procera and L. rachodes
1 G. Massee, " On the Differentiation of Tissues in Fungi," Journ. Roy. Micr.
Soc., 1887, p. 205.
Vide infra, Chap. XIX.
44
RESEARCHES ON FUNGI
which, owing to their large size and striking form, attract general
attention as they come up in open woods (Fig. 14). The pilei
consist of broad plates which are often as much as 20 cm. in
diameter and raised 25 cm. above the ground. The place of
attachment of the stipe to the pileus flesh is very high, so that
it is evident that it must be situated 1-2 cm. above the centre
of gravity of the whole pileus in
large fruit-bodies (Fig. 15). The
stipe can easily be pulled out
from the pileus, and after its
removal one may observe that it
has a flattened top. The free
pileus can again be set on the
upright stipe. If, when this has
been done, one tilts the pileus
by pressing down one side of
it with the finger and then lets
it go, it swings back into its
original horizontal position. This
could not happen if the centre
of gravity of the pileus were in
any other situation than that of
stable equilibrium. Whilst a
fruit-body is growing in nature,
so far as I have observed, the
pileus is fairly firmly fixed
upon the stipe, and does not
swing appreciably about its place
of attachment during winds.
However, to what extent the peculiar position of its centre of
gravity enables it to take up and maintain its most stable position
during expansion, still remains to be investigated.
The oldest function of the centric stipe, from the phylogenetic
standpoint, is undoubtedly that of providing a free space between the
pileus and the ground, so that the falling spores may be carried off
by lateral movements of the air. A space of this kind is already
present in such primitive fruit-bodies as those of Craterellus cornu-
FlG. 14. Lepiota procera the Parasol Fun-
gus. Fruit-body growing among grass.
Photographed at Sutton Park, War-
wickshire, by J. E. Titley. | natural
size.
THE GILL-CHAMBER 45
copioides, one of the Thelephoreoe, in which the hymenium is
smooth and not yet produced into tubes, teeth, or gills. The
length of the stipe in a few very tiny fruit-bodies is not
much more than a single centimetre, but in general it varies
from 5-12 cm. In different species it appears to bear some rela-
tionship to the size of the pileus and the usual nature of the
environment. In a single species the stipes of individual fruit-
bodies are often longest when development has taken place in
badly lighted places. The power of adjustment in response to
conditions of light doubtless finds its significance in the advantage
gained from raising up the pileus above surrounding obstacles.
In most species the stipe does not elongate when once the gills
have become outstretched, but in Coprinus comatus it goes on
FlG. 15- Lepiota procera. Section showing mode of attachment of the pileus
to the stipe. natural size.
lengthening during the whole period of spore-discharge, so that
at the end it is often 30 cm. long. A good explanation can be
found for this exception to the general rule, but it will be more
conveniently dealt with in Chapter XIX., where the Coprinus type
of fruit-body is described in detail.
In resupinate, dimidiate, and most fruit-bodies with centric
stipes, the gills are exposed from their earliest appearance. Guided
by this fact, we may regard the formation of a distinct gill-chamber,
such as occurs in the genus Amanita, Psalliota, &c. (Fig. 19),
as one of the later developments in the evolution of Agarics.
The significance of this structure is probably to be found in the
advantage derived from protecting the gills from insects, parasitic
fungi, and other enemies until the last possible moment, when
their expansion and free exposure to the air, for the purpose of
46 RESEARCHES ON FUNGI
liberating spores, becomes absolutely necessary. Some Mushrooms
which were grown for my purposes on a bed of horse manure,
whilst still shedding spores, were found to have their gills infested
with tiny animals, possibly Acarineae. These, when running about,
doubtless displaced a great number of spores, and probably also
used many of them as food. The extended velum partiale must
be an admirable means of keeping such creatures as these away
from the young gills, until, by its rending during the rapid
expansion of the pileus, the gill-chamber is broken open. A part
of the velum is often left on the stipe in the form of a more or
less pronounced ring, as in Coprinus comatus (Fig. 70, p. 199),
whilst in Amanita muscaria and allied species (Fig. 75, p. 212),
it hangs down in the form of a curtain. In the latter instance,
its position is such that it does not seriously interfere with the
falling spores as they are being carried oft' by air movements.
It is the extreme thinness and flexibility of the velum which
permits of its falling into the most unobstructive position when
it can no longer be of any service to the fruit-body.
CHAPTER IV
ADJUSTMENTS OF FRUIT-BODIES IN THE INTERESTS OF SPORE-
LIBERATION LENTIN US LEPIDEUS, PSALLIOTA CAMPESTRIS,
POLYPORUS SQUAMOSUS, COPR1XUS PLICATILIS, COPRINUS
NIVEUS, A^Tt COPRINUS PLICATILOIDES REACTIONS OF FRUIT-
BODIES TO LIGHT AND GRAVITY THE PROBLEM OF- PILEUS
ECCENTRICITY GEOTROPIC SWINGING RUDIMENTARY FRUIT-
BODIES
IN order to obtain a more precise knowledge of the means
whereby, and the extent to which, a fruit-body is able to adjust
itself so as to bring its hymenium into the optimum position
for spore - liberation, experiments were made upon Lentinus
lepideus, Psalliota campestris, Polyporus squamosus, Coprinus
plicatilis, C. niveus, and C. plicatiloides, the sporophores of which
differ considerably from one another. The first two species belong
to the Agaricineae but occupy different habitats. Lentinus lepideus
is saprophytic on wood and often produces its fruit -bodies on
surfaces which are nearly or quite vertical, such as those of logs
and stumps ; whilst, on the other hand, as every one has observed,
the Mushroom comes up in more or less horizontal pastures,
Polyporus squamosus is a wound-parasite on trees, and is most
frequently found attached laterally to tree trunks or thick branches.
Coprinus plicatilis belongs to a highly specialised genus. Its
fruit-bodies are of small size and come up in short grass. C. niveus
and C. plicatiloides are found on horse dung.
Lentinus lepideus. The fruit-bodies developed on rotting
paving blocks removed from the streets of the city of Birming-
ham. Their reactions to external stimuli have already been
described in detail in a special paper. 1 It will therefore only
be necessary here to state those results of experiment which
bear upon our problem.
1 Buller, " The Reactions of the Fruit-bodies of Lentinus lepidens to External
Stimuli," Ann. of Bot., 1905, vol. xix. pp. 427-438.
4 8
RESEARCHES ON FUNGI
A fruit-body begins its existence in light or darkness as a
tiny papilla, directed at any angle to the substratum, but pro-
jecting more or less vertically from the surface of the stromatous
layer on which it is produced (Fig. 16, A). If developed in the
dark the papilla grows out into a long finger-like stipe, which
is perfectly indifferent to geotropic stimuli. In the course of
six weeks the stipe may attain a length of 15 cm. without showing
the least trace of a pileus (D), and sometimes it may become
branched (C). In weak light it is positively heliotropic and
FlG. 16. The forms of Lentinus lepideus. A, diagram showing the beginnings
of fruit-bodies as conical processes, c, arising on a stroma, s, developed on
wood. B, section of a normal fruit-body grown in light. C, sterile and
branched fruit-body found growing in darkness. D, sterile and finger-like
fruit-body after three weeks' growth in darkness. E, f-ection of a fruit-
body with eccentric pileus. F, G, H, and I, branched and feebly- developed
fruit-bodies grown in weak light. All J natural size.
thus reacts to this stimulus as if attempting to bring its free end
into the best illuminated position. When the tip of the stipe
is acted upon by light of sufficient intensity, it flattens and
expands in a symmetrical manner, and becomes converted into
a pileus. As soon as the development of this structure has been
initiated, a remarkable change takes place in the physiological
properties of the stipe. Whilst still barren, this was absolutely
without response to geotropic stimuli but was positively heliotropic ;
it now becomes strongly negatively geotropic and entirely loses
its power of reacting to light. The rapidly developing pileus
ADJUSTMENTS OF FRUIT-BODIES 49
thus comes to have its axis turned upwards into a vertical
position. The gills at the beginning of their development simply
grow outwards in directions which are perpendicular to the under
surface of the pileus. Their only reaction to external stimuli
appears to be that of positive geotropism, which comes into play
as soon as they have attained a certain breadth.
The turning movement which is necessary in order to bring
the planes of the gills into exactly vertical positions, in the main
is accomplished by the stipe, but for its completion the sensitive
gills are themselves alone responsible. In the work of securing
a proper orientation for the hymenial surfaces, the stipe acts as
a c6arse adjustment and each gill as a fine adjustment. In
their nature and successive action these two adjustments are
strictly analogous to those which are employed in focussing the
high power of a microscope.
The reactions to external stimuli which have just been detailed
are such that:
(1) The barren stipe grows in a manner suited to find a way
to the open air.
(2) The pileus is never developed in any space which is shut
out from daylight, and therefore of such a character that, if spores
were liberated into it, they could not be properly disseminated.
(3) As soon as a pileus has begun its development, its hymenium
can readily be placed in the optimum position by a suitable
curvature of the stipe combined with a subsequent adjustment
of the gills.
The fruit-bodies of Lentinus lepideus, when growing out from
the side of a piece of wood, to some extent exhibit the phenomenon
of eccentricity of development. In extreme cases, under cultural
conditions, the pileus flesh may become quite unilateral (Fig. 16, E).
I have shown that this is due to a morphogenic stimulus of
gravity acting upon a pileus developing upon an oblique stipe.
There can be no doubt that the reaction is advantageous in that
it permits of the fruit-body developing the chief part of its spore-
producing surface in a situation where the spores will run the
least risk of catching upon the stipe whilst making their escape.
1 Loc. tit., p. 431.
50 RESEARCHES ON FUNGI
We shall return to the problem of pileus eccentricity in con-
nection with Polyporus squamosus. It may, however, here be
pointed out that the power of response to the inorphogenic
stimulus of gravity varies much in different species of Hymeno-
mycetes. In Psalliota campestris, in Coprinus, and probably
quite generally in ground Agaricineae, it is not present at all;
in Lentinus lepideus and certain other comparatively long-stiped
Agaricinese it is slightly developed ; whilst in the relatively short-
stiped Pleurotus ostreatus and Polyporus squamosus, and in the
stipeless, bracket-shaped fruit-bodies growing on trees it is very
marked.
From the above it seems clear that the fruit-bodies of Lentinus
lepideus possess in a high degree the power of adjusting themselves
in a manner suited to their environment. In nature it sometimes
happens, as I have once observed, that a fruit-body begins its
development on the underside of a log or other mass of wood.
Even then it can still succeed in placing its gills in their optimum
position.
Psalliota campestris. Mushrooms were first of all studied as
they came up under natural conditions in a large pasture. The
actual amount of curvature which the stipes of the fruit-bodies
investigated had undergone in extreme cases during development
may be gathered from Fig. 17, in which some field sketches have
been reproduced. The curvatures had been sufficient to place
the planes of all the pilei in a horizontal position. However, in
older Mushrooms, it was found that the stipe only acts as a coarse
adjustment for the gills. The latter are very thin, fairly deep,
and closely packed; and the fine adjustment of their planes in
exactly vertical directions can only be effected by their own
delicate reactions to the stimulus of gravity.
When an accident happens to a mature Mushroom so that it
becomes tilted, as is often the case in pastures where horses and
cattle are browsing, the stipe and pileus remain fixed in their
new positions. However, the gills are still in a most sensitive
condition and quickly respond to the stimulus of gravity. Each
gill grows faster on its upper side than on its lower side and
thus gradually curves downwards, so that a large part of it comes
ADJUSTMENTS OF FRUIT-BODIES 51
to look once more directly toward the earth. The rate and the
amount of the reaction depend upon various conditions, particularly
on the stage of development of the fruit-body and the amount
of the tilt. The younger the gills and the smaller the tilt, the
quicker and more complete is the readjustment hi a vertical
plane. An expanded Mushroom was placed so that the plane
of the pileus was vertical, and those gills which most nearly
occupied horizontal planes were then looked at edgewise with a
horizontal microscope. The reaction to the stimulus of gravity
FlG. 17. Psattiota campestris. Adjustment of the pileus by geotropic curvature
of the stipe. A, Mushroom grown upside down in a pot. B, two Mushrooms
grown laterally in a pot. To the left, five Mushrooms gathered and sketched
in a field. All \ natural size.
was found to begin in about an hour after the fruit-body had
been gathered and tilted. After two hours the downward cur-
vature of the free edge of the gills was marked and could be
detected with the naked eye.
When the plane of a Mushroom pileus has not been tilted up
to an angle of more than about 30, all the gills can adjust them-
selves again so as to take up vertical positions. This is permitted
by the provision of a sufficient margin of safety in their spacial
arrangement. 1 When, however, the tilt exceeds a certain amount,
i Cf. Chap. II.
52 RESEARCHES ON FUNGI
some of the gills crowd one another unduly, and only a few of the
highest have room to turn so as to give themselves the chance
of successfully liberating spores. Some Mushrooms which had
undergone symmetrical development on an artificial bed were
picked and fixed so that the planes of their pilei were set in a
vertical direction. Previous to the experiment the gills looked
downwards in the most perfect manner, and the undersides of the
pilei presented the appearance shown in Plate IV., Fig. 25. After
being placed in their new positions the gills soon reacted to the
stimulus of gravity and attempted to make the usual adjustment.
However, owing to the fruit-bodies having been tilted through an
angle of 90, this could not be successfully accomplished. A photo-
graph of the pilei, as they appeared at the end of the experiment,
is reproduced in Fig. 18. It will be seen therefrom that only a
very few gills at the top of each pileus remained separated from one
another. These liberated a few spores, which settled on the upper
sides of the extreme tops of the stipes. The rest of the gills had
become so crowded that they covered one another up. It is not
surprising, therefore, that practically no spore-deposit accumulated
on paper placed immediately below the pilei.
It seemed of interest to find out to what extent the stipe of a
Mushroom is capable of undergoing curvature when the pileus
has been placed by artificial means hi a very unfavourable position.
Accordingly, some Mushroom spawn was planted in large pots
containing horse manure covered with soil. After a few weeks
fruit-bodies duly made their appearance, but before they had
attained the size of peas their position was altered. Some of
the pots were suspended upside down and others fixed horizontally
on their sides. The soil was kept in place by the careful use of sticks
and wire netting. Under these conditions the fruit-bodies continued
to grow, and the stipe of each made an attempt to place the pileus
in the usual position. Where the pots had been inverted the
attempt proved to be almost a complete failure (Fig. 17, A), but
where the fruit-bodies grew out from the soil laterally it was
attended with a large measure of success (Fig. 17, B). Had the
fruit-bodies in the latter instance been larger and of more vigorous
growth, probably the success would have been somewhat greater.
ADJUSTMENTS OF FRUIT-BODIES
53
It is evident, however, from these experiments that the stipe of a
Mushroom has but small powers of making geotropic curvatures
FlG. 18. Psalliota campestris. Geotropic reaction of the gills. The pilei were
fixed with their planes in a vertical position. In the course of about
twenty-four hours the gills, in attempting to readjust themselves in vertical
planes, took up the positions shown in the photograph. Natural size.
when compared with that of Lentiniis lepideus, or those of species
of Mycena, Psathyrella, and Coprinus, &c. ; but owing to the fact
54 RESEARCHES ON FUNGI
that the pastures where Mushrooms grow are always more or less
horizontally disposed, large curvatures are quite unnecessary. As
a matter of fact, in extreme cases in the field, the needs of the
pileus can be fully met when the stipe bends through an angle of
only about 45 (Fig. 17, to the left).
It seems probable that the position of the pileus at its origin is
simply determined by the direction of the stromatous strand, upon
the end of which the fruit-body concerned comes to be developed.
However this may be, there can be no doubt that, as soon as the
pileus and stipe have become differentiated, the direction of further
growth of the fruit-body (excluding mechanical resistance offered
by grass, &c.) is entirely controlled by the stimulus of gravity ;
and it is to this, and to this alone, that a Mushroom owes its
characteristic position in the field. The stipe, when not yet 2 cm.
long, becomes negatively geotropic in a zone just below the pileus
flesh; whilst subsequently the gills, after partial development,
place themselves very exactly in vertical planes by growing toward
the earth's centre.
When Mushrooms come up in fields the mechanical resistance
offered by the herbage often hinders the stipe, when young, from
bending straight upwards. As the stipe gets longer and longer
the pileus becomes pushed more and more into freedom. When
this has been attained the stipe simply grows directly upwards,
but evidence of its early struggle is still left in its curved or zigzag
form (cf. Fig. 17).
Werner Magnus 1 observed that when a Mushroom comes up
on a sloping bed so that it catches in the manure and has to push
up against it, the stipe becomes unusually long whilst the pileus
remains small. He also found that when a young pileus is pre-
vented from expanding by means of a ring of gypsum, its growth
practically ceases and the stipe attains a quite abnormal length.
This peculiar correlation in growth between pileus and stipe in
nature probably sometimes helps to determine the form of Mush-
rooms, for these occasionally are to be found pushing their way
1 W. Magnus, "Ueber die Formbildung der Hutpilze," Archiv fur Biontologie,
Bd. I., 1906, p. 104.
ADJUSTMENTS OF FRUIT-BODIES 55
up against soil, grass, or dung, &c., in such a manner that con-
siderable resistance is ottered to the free expansion of the pilei.
The chief effect of an unusual lengthening of the stipe upon a
fruit-body as a spore-producing organ, consists in increasing the
chances of the pileus being raised to such a height that it becomes
freed from obstacles and can successfully liberate its spores.
Light gives rise in a Mushroom neither to a heliotropic nor
to a morphogenic reaction. I have been unable to detect any
heliotropic curvatures of the stipes of fruit-bodies grown on artificial
beds of horse manure, and a special experiment with wild Mush-
rooms also gave negative results. Eight pieces of turf, containing
Mushrooms in an early button stage of development, were taken
up from a field and placed in a room in such a way that the
buttons were well lighted on one side and in strong shadow upon
the other. However, the stipes grew up vertically and exhibited
no signs of bending toward the source of light. That Mushrooms
do not give a morphogenic reaction to illumination may be deduced
from the fact that they develop in form equally well in a perfectly
dark cellar and in a sunlit field.
The development of the fruit-bodies of Lentinus lepideus is
controlled by light and gravity in succession, whilst those of
Psalliota campestris react to gravity alone. This difference
seems to me to be connected with the diversity in the habitats
of the two species. Lentinus lepideus is a wood fungus. The
orientation of the surface of its substratum is indefinite, and may
be most varied in respect to the fruit-bodies. Response to both
light and gravity under these circumstances is, as already explained,
of distinct advantage. On the other hand, Psalliota campestris is
a ground fungus. The orientation of its substratum is in so far
definite that the surface is on the average horizontal. This being
so, when a fruit-body has ouce begun to form on the surface of
the ground, a negative geotropic reaction alone is sufficient to
enable the stipe to raise the pileus and bring it into the optimum
position. Hence, we find that the development of the Mushroom
is regulated from without simply by the stimulus of gravity. No
advantage would be gained by sensitiveness to light, and indifference
towards it is therefore easily understood.
56 RESEARCHES ON FUNGI
The adjustments by which the hy menial surfaces are placed in
the optimum position for spore-liberation in the Mushroom are no
less than four in number, and may be summed up as follows :
(1) Turning the pileus into an erect position by an upward
curvature of the stipe ; (2) raising the pileus several centimetres
above the ground by growth in length of the stipe ; (3) placing
the gills with their long axes horizontal by an expansion of the
pileus (Fig. 19); and (4) setting the planes of the gills in hori-
FlG. 19. Psalliota arvensis. a-d, sections of four fruit-bodies showing suc-
cessive stages in the raising of the gills into a horizontal position by the
expansion of the pileus. At a the gills are still enclosed in the large gill
chamber. All natural size.
zontal positions by the turning of the gills themselves about their
directions of attachment to the pileus flesh. Whilst the erection of
the pileus and the turning of the gills coarse and fine adjustments
respectively are controlled by the external stimulus of gravity, the
raising of the pileus and its expansion are, doubtless, due to internal
developmental forces alone. Proof of the latter statement seems to
be afforded by the fact that Mushrooms can elongate their stipes
and expand their pilei when growing upside down in the dark
(cf. Fig. 17, A).
Polyporus squamosus. 1 P. squamosus, the Great Scaly Poly-
1 Cf. Buller, "The Biology of Polyporus sqtiamosus, a Timber-destroying
Fungus," Journ. of Economic Biology, 1906, vol. i. pp. 101-138.
ADJUSTMENTS OF FRUIT-BODIES 57
porus or Saddle-Back Fungus, is one of the best known European
species of tree-destroying fungi, and it is also found in the United
States and Canada. Its large ochraceous fruit-bodies, checkered
with brown scales above, are frequently to be seen projecting as
brackets, either singly or in groups, from trunks and branches of
living trees in woods, parks, and gardens (Figs. 1 and 4-7, pp. 8,
28, 29, 32, and 33 ; also Plate V.).
For the purpose of studying the development of the fruit-bodies
under special conditions, several logs which had been half destroyed
by the mycelium were procured and removed to an experimental
greenhouse. As this was conveniently provided with a dark-room,
it was possible to grow the sporophores in total darkness as well
as in ordinary daylight.
When the mycelium of the fungus is about to produce fruit-
bodies, it grows out on to the surface of the tree trunk or branch,
usually at a place where the bark has been removed. It there
forms a more or less rounded, but somewhat irregular, stromatous
knob of firm consistency (Plate V., Fig. 36). When this knob
has reached a certain size and is less than twenty-four hours old,
one, or usually several, bluntly conical processes arise upon it,
grow straight outwards from its surface, and thus come to point
in different directions in space (Fig. 21, A; Plate V., Figs. 31
and 37). The development up to this point takes place about
equally well under all conditions of light. It is noticeable, however,
that the knobs produced in darkness are quite white and smooth,
whereas those arising in full daylight are somewhat brown and
scaly.
When fruit-bodies develop entirely in the dark, the conical
processes on the stromatous knobs grow outwards into long sterile,
finger-like columns which are usually curved or twisted, frequently
flattened toward their ends, and in many cases branched. In the
course of three weeks, vigorous fruit-bodies may attain a length
of 15 cm. and come to resemble a stag's horn (Fig. 20). The
branches grow at their apices only ; their ends are pure white,
whilst the older parts become deep black, like the base of the
stipes in fruit-bodies developed in daylight.
The horn-like processes just described appear to be unaffected,
58 RESEARCHES ON FUNGI
in respect to their direction of growth, by both gravity and light.
The branches grow in the dark in curves which take the most
FlG. 20. Fruit-body of Polyporus squamosus developed on a log in entire
absence of light, three weeks old. It is branched and sterile : there are
no signs of a pileus. Cf. Figs. 1, 4, and 5. Reduced to f natural size.
varied directions in space, and show no definite indications that
they are either positively, negatively, or transversely geotropic.
Light from a small hole cut in the dark-roorn door was allowed
to fall obliquely on to the log upon which some almost fully
ADJUSTMENTS OF FRUIT-BODIES 59
developed sterile fruit-bodies were growing. After varying the
intensity of the light considerably and extending the experiment
over many days, I was unable to detect any change in the direction
of growth of the branches in response to the illuminating rays.
In being unprovided with heliotropic properties, the sterile fruit-
bodies of Polyporus squamosus present a marked contrast with
those of Lentinus lepideus.
The formation of the pileus is brought about entirely by a
morphogenic stimulus of light. To this kind of stimulus the
young fruit-bodies (although not the older sterile ones)' are re-
markably sensitive, for, when some of them were temporarily
exposed to daylight for only a single hour and then replaced
in the dark-room, they subsequently produced pilei.
In the development of a pileus, light is only of real importance
in the very initial stages. Some fruit-bodies were grown on a
log in ordinary daylight. When they were about two days old and
the pileus on each was yet in a most rudimentary condition, the
log was placed in the dark-room. The fruit-bodies, thus shut
off from all illumination, continued their development, attained
a considerable size, produced hymenial tubes, and liberated millions
of spores. Light therefore appears to give a sufficient morphogenic
stimulus to a fruit-body within a comparatively lew hours after
the latter has come into existence. It unlocks developmental
forces which, when once set free, become independent of the
liberating agent.
In the light, the ends of the conical processes after flattening
or becoming depressed, quickly expand to form small pilei (Fig. 21,
B and C ; Plate V., Figs. 32 and 33). That part of a process which
bears the pileus we shall now refer to as the stipe.
The stipe owes its position in the first instance to accident.
However, it quickly becomes negatively geo tropic and makes an
upward curvature so as to bring the top of the pileus into a
horizontal plane (Fig. 21, D). When this has taken place the
pileus becomes diageotropic, and now expands rapidly in a direction
parallel to the earth's surface (Fig. 21, E; Plate V., Figs. 33 and 34).
Subsequently hymenial tubes develop on its under surface; they
are positively geotropic and grow vertically downwards. These
6o
RESEARCHES ON FUNGI
diverse geotropic phenomena were elucidated by placing very young
or half-grown fruit-bodies in the dark, tilting them out of their
normal positions, and watching their development. In the absence
of light, stipes curved upwards, hymenial tubes grew downwards,
and the pileus flesh extended itself horizontally (Plate V., Fig. 41).
FlG. 21. Polyporux squam^sus. The embryology of fruit-bodies with eccentric
pilei. A-E, vertical sections showing successive stages in development. A,
a stromatous knob upon which a conical process has arisen. B and C show
the origin of the pileus by depression and lateral expansion of the tip of a
conical process. At D the stipe has made a geotropic curvature so that the
top of the pileus has become almost horizontal. The pileus has now begun
its eccentric development. E is a fully-grown fruit-body. Its pileus is very
eccentric and has developed hymenial tubes. F-I, young fruit-bodies seen
from above. The pilei F and G correspond to those seen at B and C. H, a
young fruit-body in which an anterior half of the pileus, a, may be distin-
guished from a posterior half, y. The stipe, *. is laterally placed as at D. I, a
young fruit-body in which the anterior half of the pileus, x, is growing
rapidly, whilst the posterior half, y, has ceased development, s, the stipe.
All natural size.
In most fruit-bodies the stipe is lateral (Fig. 4, p. 28), in a few
more or less eccentric (Plate V., Fig. 426), and in rare instances
quite centrally situated, like that of a Mushroom (Fig. 22). An
attempt will now be made to account for this remarkable variability
of form.
ADJUSTMENTS OF FRUIT-BODIES 61
The shape of the pileus seems to be partly decided by the
direction of the conical process upon which it develops. When
a conical process happens to point vertically upwards (as it very
rarely does), the stipe to which it gives rise is vertical and the
FlG. 22. Polyporus squumosus. Under surface of a large fruit-body with a central
stipe. J natural size.
pileus horizontal from the moment of their differentiation (cf.
Plate V., Fig. 35). Under these circumstances, since the internal
developmental forces are symmetrically disposed, the pileus simply
grows at an equal rate all round its periphery. In response to
a diageotropic stimulus, it spreads itself out in a horizontal plane.
62 RESEARCHES ON FUNGI
When the fruit-body becomes full-grown, it thus comes to have
an umbrella shape like that of an upright, expanded Mushroom
(Fig. 22). On the other hand, if the axis of the conical process
upon the stromatous knob happens to be inclined upwards, let
us suppose at an angle of 45, then the fruit-body at its origin
is obliquely set (Fig. 21, B; Plate V., Fig. 32). The young stipe
receives a directive stimulus from gravity and grows faster below
than above. It therefore gradually bends upwards and only stops
this movement when the top of the pileus has been turned into
a horizontal position (cf. Fig. 21, D). We may suppose that a
morphogenic stimulus of a special kind is conducted to the pileus
from the stipe whilst this is making its geotropic curvature. As
a reaction to this stimulus the pileus undergoes a physiological
change : its developmental forces become reorganised. It can
now be said to have two distinct halves differentiated from one
another. One of them may be referred to as anterior in position
and the other as posterior. The former is always the half which
is furthest away from the base of the stipe and the latter the one
nearest to it (Fig. 21, F-I). The anterior half undergoes rapid
and considerable expansion, but the posterior half soon discontinues
its development. In the mature fruit-body, in this instance, the
pileus has a unilateral position like that shown in Fig. 4, p. 28, and
in Fig. 21, E. Slightly eccentric pilei are formed when their stipes
at the beginning happen to be nearly vertical but not quite. The
less oblique the stipe, the less will be the physiological differ-
entiation induced by the stipe in the two halves of the pileus,
and the more nearly in the end will the fruit-body approach the
umbrella form. If the foregoing correctly represents what takes
place during development, it follows that the form of a fruit-
body is indirectly controlled by gravity. The radial symmetry
of the pileus is only interfered with when the stipe has responded
to a geotropic stimulus. The degree of eccentricity of the one
part seems to be proportional to the amount of curvature undergone
by the other part.
Since the unilateral pilei of fruit-bodies growing on the trunks of
trees are directed away from the trunks or branches, one might be
inclined, without investigation, to think that this is due in part to
ADJUSTMENTS OF FRUIT-BODIES 63
the effect of light. However, it was found that when very young
fruit-bodies which had just formed pilei in the light were placed in
various directions in the dark-room, they continued their develop-
ment and took up situations relatively to their substratum similar to-
those observed in nature (Plate V., Fig. 41). Both the position
assumed by, and the degree of symmetry of, a fruit-body are
governed by gravity alone. However, there can be little doubt
that light exerts a tonic influence upon the pileus during its develop-
ment. When a half-grown fruit-body which had been exposed to-
light in the open for about a week is placed in the dark so that the
plane of its pileus is vertical, the flesh grows sharply through a right
angle at its upper margin, and thus the new part takes up a position
parallel to the earth's surface. In this case the diageotropism of the
pileus is very marked. If a very young fruit- body which has
developed in the light for only two or three days (cf. Plate V.,
Figs. 32 and 33) is set in darkness, the pileus often grows obliquely
upwards for some time and its diageotropism is but poorly displayed
(Plate V., Fig. 42, /). If, in response to a light stimulus of about
an hour's duration, a pileus develops upon a branch of a stag's-horn-
like structure which is still growing vigorously and is looking
upwards, it becomes trumpet-shaped in the dark (Plate IV., Figs. 40
and 42, d and e). If it responds to the stimulus of gravity at all, it
only gives an obliquely geotropic reaction. On the other hand, a
symmetrical pileus grown throughout in daylight has a very flat top
and is evidently strongly diageotropic (cf. Fig. 4, p. 28, and Plate V.,
Fig. 40). It thus appears that the geotropic reaction of the pileus
flesh is partly determined by the amount of illumination to which
a fruit-body is exposed.
When a stag's-horn-like structure has grown for two or three
weeks in the dark, and has almost attained its full extension, it can
be caused to form patches of hymenial tubes on its under surface by
exposure to sufficient daylight (Plate V., Figs. 38 and 39). The
branched fruit-body thus produced presents a remarkable contrast
with such normal ones as are found on trees.
A feebly developed, trumpet-like fruit- body which came to-
maturity in weak light (cf. Plate V., Fig. 40) produced hymenial tubes
both on the lower and the upper surfaces of its pileus (Fig. 23). A
64 RESEARCHES ON FUNGI
similar disposition of hymenial surfaces has been observed in nature
by others for Hydnum repandum. Two fruit-bodies of Polyporus
varius which were recently brought to me, had a quite normal
appearance except for the fact that very shallow hymenial tubes had
developed on the tops of the pilei. The cause of the formation of
these monstrosities still remains to be elucidated. The abnormal
pileus of P. squamosus first of all developed hymenial tubes on
its under surface. As it continued to enlarge it gradually fell by
FlG. 23. Polyporus squamosus. Section through part of a pileus
with hymenial tubes on the upper as well as on the lower
surface. About natural size.
its own weight, until on one side its plane looked downwards at an
angle of about 45. At this stage a new layer of tubes grew upwards
in an irregular manner on the pileus top. It seems likely that the
unusual displacement of the fruit-body in some way initiated this
development.
Owing to their wonderful power of undergoing unilateral de-
velopment, the fruit-bodies of Polyporus squamosus are admirably
adapted for securing a successful liberation of their spores. The
hymenial tubes come to look downwards upon an open space as far
from the tree trunk as possible, and the stipe is so placed that it
ADJUSTMENTS OF FRUIT-BODIES 65
cannot hinder the fall of the spores, or their dispersion by the
wind.
We may now sura up the adjustments made in a developing
fruit-body by which the hymenial surfaces are placed in the
optimum position for spore-discharge. They are five in number :
(1) Slight raising of the pileus by growth in length of the stipe;
(2) placing the top of the pileus in a horizontal plane by a curvature
of the stipe ; (3) growth of the pileus parallel to the earth's surface ;
(4) growth of the pileus with a symmetry suited to the position of
the stipe ; and (5) the downward growth of the hymenial tubes.
The first of these adjustments is doubtless due to internal develop-
mental causes alone, but the other four are controlled by gravity.
A fruit-body of Polyporus squamosus owes the origin of its pileus
to the stimulus of light, and in addition it responds in four different
ways to the stimulus of gravity. On the other hand, a Mushroom is
indifferent to light and has only two reactions to gravity. The
difference between the two species in the number of responses made
to external stimuli is correlated with the fact that the one fungus
grows on a tree and the other on the ground. In each case the
dependence on external forces seems to be of the simplest kind
to meet the requirements of the environment in a successful
manner.
Coprinus plicatilis. The small fruit-bodies of this species were
found coming up on a lawn. A single specimen with its surrounding
turf was taken indoors, and immediately placed on its side in the
position shown at a in Fig. 24. In order to prevent too rapid
transpiration, the turf was sprinkled with water and covered with an
inverted glass dish. In two hours the plane of the pileus had been
turned by the stipe through an angle of 60 (6), and in three hours
it had become almost horizontal (d). To my surprise, however, the
stipe continued its curvature for an hour, until the pileus had become
tilted quite 20 too much (/). It then began to bend back again, and
in the course of a further hour the pileus was returned for the second
time to its optimum position (k). The curvature of the stipe, how-
ever, still continued, and became overdone to the extent of about
15 0). Again the stipe rebent itself, and for the third time the
pileus became erect (m). After this the stipe overdid its curvature
RESEARCHES ON FUNGI
p was
f the
FIG. 24. Coprinui! plicatilia. Geotropic swiu-in- and adjust-
ment of the pilens in space. A fruit-body was placed
in the position shown at o, and after 2 hours it had
assumed the position shown at b. The sketches b-o were
made in succession at intervals of half-an-hour.
drawn 1 hour after o. The plane of the base o
pilens became horizontal after 3 hours (d), much over-
tilted after4 hours( f), again horizontal after 5 hours(/<),
much over-tilted asjaiu after 6-6'5 hours 0' and fc). asjain
horizontal after 7'5 hours, very slis-htly over-tilted for
the last time after 8 hours (n), and finally horizontal
after 8'5 hours (o). The horizontal position was still
maintained after 9'5 hours (p). Natural size.
once more to the extent
of about 2 (n). It then
rebent itself for the fourth
and last time, and brought
the plane of the pileus
into a horizontal position,
where it finally remained
(o and p). The sketches
6 to o in Fig. 24 were all
made in succession at in-
tervals of half-an-hour.
The formation of a black
spore- deposit beneath the
fruit - body was noticed
subsequently to the
stage j.
The physiological
swinging of a fruit-body
of Coprinus plicatilis
about its objective and
final position forcibly
reminds one of the oscil-
latory movements of a
pendulum under the
action of gravity. It
finds its parallel in the
well-known geotropic re-
sponses of shoots in the
Phanerogamia. We are
thus provided with an-
other striking piece of
evidence that protoplasm
has the same fundamental
characteristics through-
out the vegetable king-
dom. A further investi-
gation upon the pheno-
ADJUSTMENTS OF FRUIT-BODIES 67
menon of geotropic swinging will be recorded in connection with
an account of Coprinus plicatiloides.
The adjustments of a fruit-body of Coprinus plicatilw, by means
of which the successful liberation of the spores is secured, are three
in number : (1) The erection of the pileus by the bending of the
stipe ; (2) the raising of the pileus by elongation of the stipe ; and
(3) the adjustment of the gills by the expansion of the pileus. The
gills do not appear to be positively geotropic. Not only are they
small in size, but they split from above downwards in a manner
peculiar to many species of Coprinus. When the pileus expands,
they open out like the folds of a parasol. It is clear that the
hymenium is sufficiently adjusted to a suitable position by the
curvature of the stipe and the expansion of the pileus. A reaction
of the gills to gravity, like that which occurs in the Mushroom,
would be quite unnecessary. The relations of the fruit-bodies with
light were not investigated.
For the Coprini generally, there appears to be an absence of
geotropic response in the gills. This peculiarity is correlated with a
very special mode of spore-liberation which will be described in
detail in Chapter XIX.
Coprinus niveus. This species is coprophilous, and is frequently
found in the autumn upon horse dung in fields. The fruit-bodies
which are snowy white, make their appearance at any place on the
free surface of the dung balls. At first they are strongly heliotropic
and with unilateral illumination simply grow toward the source of
light. This heliotropic response enables the stipes to push their
unexpanded and conical pilei outwards between, or from under, the
dung balls into the open. Growth toward the source of light con-
tinues until the stipe is some 3-4 cm. long. Shortly before the
pileus begins to expand, the top of the stipe ceases to be heliotropic
and becomes negatively geotropic: it makes a new curvature and
grows vertically upwards. This adjustment causes the whole pileus
with its gills to be placed in the requisite position for the successful
liberation of spores. Some horse dung obtained from a field was set
so that the fruit-bodies found growing upon it looked directly up-
wards. The oblique light from a window caused the stipes to make
a heliotropic curvature (Fig. 25, to the left). Afterwards, when the
68 RESEARCHES ON FUNGI
pilei began to expand, the stipes ceased to grow toward the window,
but instead grew vertically upwards. On the right side of Fig. 25 is
shown the same group of fruit-bodies as on the left after twelve
hours' further development. By comparing the figures, the change
FIG. 25. Copnnua nivcus. Adjustments of the pileus in space. The fruit-bodies
grown on horse dung received unilateral illumination from a window. The
young stipes, as shown on the left, made heliotropic curvatures. On the right
the fruit-bodies are twelve hours older than on the left. As soon as the pilei
began to expand, the stipes, in response to a geotropic stimulus, grew vertically
upwards. Stages in the raising of the pileus by elongation of the stipe, and in
the expansion, auto-digestion, and rolling up of the pileus are also to be seen.
Natural size.
which took place in the direction of growth of the stipes may be
readily realised.
The expansion of the pileus separates the gills from one another,
and causes the hymenium to look downwards in a manner similar to
that described for Coprinus plicatilis. Here, again, the gills do
not require to adjust themselves in vertical planes by means of a
geotropic stimulus. The part played by the ' : deliquescence " of the
gills and the folding of the pileus rim over the top of the pileus
ADJUSTMENTS OF FRUIT-BODIES 69
in the process of spore-liberation will be sufficiently discussed in
Chapter XIX.
The adjustments of the fruit-bodies of Coprinus nivens in the
interest of successful spore-liberation may be summed up as follows :
(1) Heliotropic curvature of the stipe, which causes the pilei to be
brought out of crevices in the substratum into the open ; (2) erection
of the pileus by a negatively geotropic curvature of the stipe;
(3) raising of the pileus by elongation of the stipe ; (4) adjustment
of the gills by the expansion of the pileus ; and (5) deliquescence
of the gills and the folding of the pileus rim over the tqp of the
pileus.
Coprinus plicatiloides, Buller. 1 This species, like the foregoing
one, is coprophilous and occurs on horse dung. Its fruit-bodies are
often very tiny and rank among the smallest in the whole group of
the Agaricinese. I have seen specimens less than 1 cm. long and with
the expanded pileus only 2 mm. wide. The average length of the
stipe is about 3 cm. and the width of the pileus about 5-6 mm., but
in large individuals, produced on sterilised horse dung, these dimen-
sions may be doubled. The fruit-bodies are extremely delicate and
can only stretch their stipes and expand their pilei under very moist
conditions. When exposed to moderately dry air they wither up in
a few minutes. The life-history of the fungus requires but little
time for its completion. Some sterilised horse-dung balls were
infected with spores and kept in a warm room. On the tenth day
after infection young fruit-bodies made their appearance, and by the
fourteenth day spores were being freely liberated.
The fruit-bodies of C. plicatiloides react in succession to the
stimuli of light and gravity in the same manner as those of
C. niveus. One evening, a fruit-body which had begun to grow
vertically upwards from its substratum was covered over with a
cap of stanniol paper opened at one end (Fig. 26, A and B). During
the night the upward growth continued. Next morning, in response
1 This name has been given for the sake of convenience in reference. The
fungus was obtained at Winnipeg. I have not been able to identify it with any
described species, but it much resembles Coprinus plicatilis. Its disc is depressed
at maturity, as in C. plicatilis, but it is narrow instead of being broad. The gills
are not attached to a collar, and the spores are oval.
RESEARCHES ON FUNGI
to unilateral illumination, the stipe made a positive heliotropic
curvature, and oblique growth toward the source of light went on
all day (C and D). When darkness supervened, the stipe still con-
tinued to grow in the direction it had taken up during the previous
day. Toward morning on the next day, it gradually curved verti-
cally upwards, thereby indicating that it had become geotropically
sensitive. After the stipe had been growing away from the earth's
centre for about three hours, the pileus expanded in a horizontal
plane and discharged its spores (E). Spore- discharge lasted for
about an hour and a half. Soon after its completion the fruit-body
FIG. 26. Coprinus pHcatiloid.es. Avoidance of an obstacle by successive reactions
to the directive stimuli of light and gravity. A, paper cap shown in B-E in
section. B, young fruit-body covered with'the paper cap on the afternoon of
the first day. C, the fruit-body at daybreak on the second day : the arrow
shows the direction of the chief incident rays of light D, the fruit-body
at the end of the second day. E, the fruit-body about noon on the third
day. Natural size.
collapsed. The successful avoidance of an obstacle and subsequent
uplifting of the pileus, as illustrated by the experiment just recorded,
affords excellent evidence of the biological importance of the re-
actions of the fruit-body to external stimuli.
In order to test the sensitiveness of the stipe to the stimulus of
gravity, a vertical fruit-body, attached to its dung ball, was tilted
into a horizontal position. A distinct reaction was noticed in about
1 minutes, and the pileus was raised into the erect position again in
1 hour 15 minutes. By using specimens a little less developed, a
greater sensitiveness was observed : the plane of the base of the
pileus was turned from the vertical to the normal horizontal position
ADJUSTMENTS OF FRUIT-BODIES 71
in 45 minutes. After further practice in handling the material and
in making observations, I found a fruit-body which curved upwards
through a right angle in 17*5 minutes. It gave a distinct macro-
scopic reaction to the stimulus of gravity after 3 minutes' stimulation,
turned through an angle of 10 in the first 5 minutes, and through a
further angle of 80 in the next 12-5 minutes. The pileus, therefore,
was turned through almost a complete right angle with an angular
velocity greater than that of the minute hand of a clock. This
angular velocity is far greater than that known for any Phanerogam
or, indeed, any other plant when stimulated by gravity. For a stem
to turn upwards through a right angle several hours are usually
required, whereas, as we have seen, the stipe of Coprinus plicatiloides
can perform this movement in 17'5 minutes. The latent period for
roots the time required for the commencement of curvature after
continuous geotropic stimulation is, according to Moisescu, 1 who
experimented on Lupinus albus, Cucurbita, &c., at least 15 minutes
when one observes with the naked eye. On the other hand, the
stipe of the Coprinus made a distinct curvature in 3 minutes. The
remarkable rapidity of the geotropic reaction in the fungus is com-
parable with the reactions of tendrils to the stimulus of touch. 2
Moisescu 3 states that with the microscope he could detect a
slight downward curvature of certain roots after one minute of
stimulation. In an experiment in which a fruit-body was tilted to an
angle of 45 and the stipe supported on a rest so as to prevent its
initial sagging from the weight of the pileus, a distinct upward
curvature was observed with a horizontal microscope of low magnifi-
cation in one and a half minutes. Probably further experiments
1 Moisescu, " Kleine Mitteilung iiber die Anwendung des horizontalen Micro-
skopes zur Bestimmung der Reaktionszeit," Ber. d. deutschen bot. Gesell., Bd. XXIII.,
1905, p. 366.
2 The movements of very sensitive tendrils in certain species are even more
rapid than that observed for the stipe. Thus, after rubbing the inner side of a
tendril of a Cucumber and placing the rubbed surface in contact with a stick, I
observed that the tendril made a half-turn round its support in five minutes, a
whole turn in ten minutes, and one and a half turns in twenty minutes. The
temperature was 85 F. The mean angular velocity of the tendril for the first
ten minutes was 36 times greater than that of the stipe, although after twenty
minutes it had become only 5'5 times greater.
3 Moisescu, loc. cit.
72 RESEARCHES ON FUNGI
would show that the latent period for the fungus stipes is quite as
short, if not shorter, than that for roots.
Already, in describing the adjustments of Coprinus plicatilis,
we have become acquainted with the fact that a stipe which has
been displaced from a vertical position performs a series of geo-
tropic oscillations before again coming to rest. A similar pheno-
menon occurs with Coprinus plicatiloides, but in this species the
oscillations sometimes take place in surprisingly short intervals of
time. In one experiment a fruit-body was
moved from a vertical to a horizontal posi-
tion whilst the stipe was rapidly growing in
length (Fig. 27, a). The plane of the base
of the pileus became turned upwards through
a right angle in 1 hour and 15 minutes (6).
However, the curvature of the stipe was con-
tinued for half-an-hour until the pileus plane
had become tilted up to a maximum angle
of 41 (c). The stipe then began to make a
FIG. 27. Geotropic reaction reverse curvature, and in the course of an
of the stipe of Coprinus . , . .. . , .. -,
The fruit- hour and a halt 'gradually regained its ver-
tical P sition - Its oscillatory movements
position, a. b-d, subse- then ceased. The pileus, which at this stage
quent positions of the
fruit-body : b, after i hr. had already become partially expanded, then
15 mins. ; c, after 1 hr. j ., i r , . u .LIT
45 mins. ; d, after about spread itself out in a horizontal plane and
oAhe plaSTof the base liberated its s P ores ( d )' Ifc seems somewhat
of the pileus, shown at c, remarkable that, in the attempt to bring the
was 41. Natural size.
pileus into its optimum position for liberat-
ing the spores, although the first geotropic reaction was so remark-
ably overdone, the second should have resulted in such complete
success. The second adjustment was accompanied by, and probably
affected by. the opening of the pileus.
The most interesting case of geotropic oscillations was observed
with the already mentioned very sensitive fruit-body which turned
upwards through a right angle in 17'5 minutes after displacement.
The stipe executed no less than five oscillations about its normal
position (Fig. 28). The successive geotropic supracurvatures were
28, 8, 3, 1, and 0. The swing past the normal position in each
ADJUSTMENTS OF FRUIT-BODIES
73
oscillation was therefore about one-third of the previous swing up
to the normal position. Each succeeding oscillation was made in
less time than its predecessor, and the whole series of movements
was completed in an hour and a quarter. In making observations
upon the amount of curvature, advantage was taken of the fact
that the plane of the base of the pileus, viewed horizontally, appears
as a straight line (cf. Fig. 27). The tilt of this line was measured
by placing a sliding lever parallel to it, and then reading off the
\
\
6(1
'
\
{ft
\
( (f
\
7(T
\
1
\
1(1
1
\
Q
*
\
s
^
^
I
M<
8
a.
I
16
\
Q
36
JX
Jt
^
u
V
**
n o
\
/
10'
V-*.
^x
t.o
FIG. 28. Eesults of observations on the movements of a fruit-body of Coprinus plicati-
loidcs about its normal position in response to the stimulus of gravity. The fruit-
body at the beginning of the experiment was turned from a vertical in to a horizontal
position. The ordinate gives the inclination of the axis of the end of the stipe to
the vertical in degrees and the abscissa the time in minutes. The curve drawn
through the observation points shows that the fruit-body executed a series of
damped oscillations.
deflection from a horizontal plane by means of a surveyor's pro-
tractor. Since the axis of the end of the stipe is always perpen-
dicular to the plane of the base of the pileus, the divergence of
the latter from the horizontal gives the divergence of the former
from the perpendicular. The fruit-bodies, attached to their horse-
dung balls, were kept in a covered glass vessel in order to prevent
loss of moisture. The laboratory temperature was 20 C. The
deflections of the stipe from the vertical at successive periods of
74 RESEARCHES ON FUNGI
time are plotted out in Fig. 28. The resulting curve is one of
damped oscillations, roughly resembling that of a pendulum swing-
ing in a viscous medium. Some of the results plotted do not lie
on the curve. I have reason to suppose that this is due not to
irregularities of growth, but to errors in making the observations.
Greater accuracy, doubtless, would have been obtained if an assistant
had recorded times whilst I recorded angles, but, unfortunately, in
the absence of help, it was necessary for me to make the two sets
of measurements by myself. Both alertness and correctness of
judgment are required in order to place a sliding lever parallel to
the pileus plane. Practice, however, enables one to make the
necessary readings with considerable precision.
In the development of the fruit-bodies in my laboratory an
undoubted periodicity was observed. A few fruit-bodies expanded
each morning and shed their spores during the mid-day hours,
usually between 12 and 3 o'clock. In properly cared for cultures I
could never find fruit-bodies opened at night. Successive crops
of mature fruit-bodies were thus produced with a diurnal rhythm.
A similar rhythm is well-known for Pilobolus ; and in Ascobolus
a few asci ripen and burst each day. The stretching of the spor-
angiophore of Pilobolus, and of a group of asci in Ascobolus, is
put off until morning, so that light may be used to direct the
growth of these heliotropic structures toward an open space. If
the orientation of the fungus guns were to take place at night, its
successful accomplishment would be simply a matter of chance.
In Coprinus plicatiloidcs the stipe is too massive a structure to
be fully developed in one morning. Its partial elongation and
curvature toward an open space in response to the stimulus of
light, take place on the day previous to spore-discharge. On the
next morning it erects the pileus in response to the stimulus of
gravity. It is clearly of advantage that the stipe shall begin to
elongate in the daytime rather than at night, for the first requisite
for the successful functioning of a fruit-body is that the pileus
shall be brought into the open. The rhythmic development of
the fruit-bodies of all the three coprophilous fungi seems, there-
fore, to be of distinct importance in facilitating the scattering of
the spores.
ADJUSTMENTS OF FRUIT-BODIES 75
A diurnal rhythm in the development of the fruit-bodies of
small and ephemeral Coprini occurs not merely in the laboratory
but also in nature. I have noticed it more particularly in the case
of Coprinus plicatilis growing on a lawn. A few fruit-bodies came
to maturity toward each noon for a succession of 20-30 days.
Worthington Smith 1 noticed the same phenomenon for Coprinus
radiatus growing on a manure heap. He states that "at seven
or eight in the evening nothing but immature plants can be seen ;
about eleven or twelve a rapid growth commences, and by two
or three o'clock in the morning perfect maturity is reached. If
the morning is moist the plants will remain in perfection till nine
or ten o'clock, but if it is dry they will not last after five or six."
According to these observations, in nature the fruit-bodies of
Coprinus radiatus may shed their spores before daylight appears.
If this is so, strong support is given to my view that the importance
of the periodic development lies, not in spore-liberation occurring
at any particular time, but in the fact that the beginning of the
stretching of the stipe is arranged to take place whilst light can
be used as a directive stimulus.
The adjustments of the fruit-bodies of Coprinus plicatiloides
in the interests of spore-liberation may be summed up as follows:
(1) Heliotropic curvature of the stipe, which causes the pilei to
be brought out of crevices in the substratum into the open ;
(2) erection of the pileus by a negatively geotropic curvature of
the stipe; (3) raising of the pileus by the elongation of the stipe;
and (4) adjustment of the gills by the expansion of the pileus.
There is no deliquescence of the gills, and on this account the
fruit-bodies of Coprinus plicatiloides have one adjustment less
than those of Coprinus niveus.
General Remarks. A number of otherwise very different copro-
philous fungi resemble one another in reacting to light. Thus we
find that positive heliotropic curvatures are made, not only by the
stipes of the Coprini, but also by the sporangiophores of Mucor,
Phycomyces, and Pilobolus, by the asci of Ascoboli, and by the
perithecial necks of Sordarite. These responses to light are adrnir-
1 W. Smith, "Reproduction in Coprinus radiatus" Grevillea, vol. iv., 1875-76,
p. 54.
RESEARCHES ON FUNGI
ably adapted to permit of organs of reproduction, which are pro-
duced on an irregularly disposed substratum, liberating their spores,
so that they may freely escape from their place of origin.
Probably all the coprophilous Coprini are heliotropic, since they
all grow on the same peculiarly irregular substratum. However
Coprinus comatus, which comes up on turf in fields, &c., appears
to be without response to light. When the fruit-bodies receive
unilateral illumination, the stipes do not make a heliotropic cur-
^^^^^___ , --I^^^^^^M^M^^M vature (cf. Figs. 69
and 70, pp. 198, 199).
As with the Mush-
room, heliotropism
would be without
advantage. The
fields in which the
fruit-bodies come up
are on the average
horizontally dis-
posed. In order to
raise the pilei, so
that they become
free from surround-
ing obstacles, re-
sponse to the stimu-
lus of gravity is all
that is necessary.
Anellaria separ-
ata (Fig. 32, p. 80)
is also coprophilous in habit, and in general form its fruit-bodies
resemble those of coprophilous Coprini. In the field the stipes are
usually vertical. When a mature fruit-body liberating spores is
tilted, the top of the stipe is still capable of responding to a geotropic
stimulus. The peculiar appearance of a full-grown fruit-body which
has been tilted and has readjusted itself is illustrated in Fig. 29.
On tilting the very small fruit-bodies of Omphalia fibula which
are to be found on lawns, &c., I have been unable to detect any
geotropic response in the narrow decurrent gills. In this species,
FlG. 29. Anellaria separata. Geotropic reaction of the
stipe. To the left is a fruit-body of a closely allied
species, Pansenlus phalaenarum. To the right are two
fruit-bodies of Anellaria separata which resembled in
form that on the left. After they had been set in
oblique positions the pilei became readjusted by curva-
tures made by the tops of the stipes. ^ natural size.
ADJUSTMENTS OF FRUIT-BODIES 77
and probably also in certain others where the fruit-bodies are
diminutive, there is only one response to gravity, namely, that
of the stipe. This is sufficient to place the tiny pilei so accurately
in the erect position that the gills look downwards and successful
spore-liberation can take place. In larger ground Agaricinese with
deep gills, e.g. the Mushroom, an extra response is requisite,
namely, that of the gills themselves. The most complex of all
Agaricineae in relation to gravity, doubtless, are certain large
species, such as Pleurotus ostreatus (Figs. 2 and 3, pp. 22 and 23),
which grow on trees and stumps. These probably have four geo-
tropic reactions similar to those already discussed for Polyporus
squafmosus ; (1) Negative geotropism of the stipe; (2) diageotropism
of the pileus flesh; (3) eccentricity of development; and (4)
positive geotropism of the gills.
It is the rule with Hymenoinycetes that the mycelium gives
rise to a great many more rudimentary fruit-bodies than can
possibly come to maturity. On a Mushroom bed one may often
observe some hundreds of such rudiments within the space of a
few square inches; and even in Polyporus squamosus the rudi-
ments are generally at least twice as numerous as the mature
fruit-bodies (Plate V., Fig. 31-34). It generally happens that a
very limited number of the rudimentary fruit-bodies obtain the
advantage over their fellows and commence to grow rapidly. The
food supply is thus drawn to them, and the unsuccessful rudi-
ments at once cease their development and become aborted. The
production of a great many rudiments at the beginning of repro-
duction increases the chance that some of them will be suitably
situated for successful development. In some species, it generally
happens that a number of rudiments continue their development
side by side, so that at maturity the fruit-bodies are more or less
crowded. The crowding in Collybia velutipes, Coprinus micaceus,
and Armittaria mellea (Fig. 30), &c., may become so excessive
that a large proportion of the spores produced are prevented from
escaping from the fruit-bodies. Such overcrowding seems to be
a distinct imperfection in fungus development.
We may summarise the general conclusion from the observa-
tions recorded in this chapter as follows. The fruit-bodies of the
7 8 RESEARCHES ON FUNGI
Hymenomycetes during development execute a set of complex
growth movements which are partly controlled by internal causes
and partly by external stimuli. These movements are correlated
with the general structure of the fruit-bodies, and with the
FIG. 30. ArmiUaria mellea. Overcrowded group of fruit-
bodies growing on a living Mountain Ash (Pints
Aucuparia}. Photographed at Sutton Park, Warwick-
shire, by J. E. Titley. About J natural size.
position of the surface of the substratum on which each species
grows. The result of the movements in all cases is to place the
hymenium in such a position that it can discharge its spores, so
that they may fall freely downwards into an open space from
which they may be carried off by the wind.
CHAPTER V
SPORE-DEPOSITS THE NUMBER OF SPORES
ALTHOUGH the spores of Hymenomycetes under ordinary circum-
stances are too small to be seen individually with the naked eye,
yet, when collected together in large numbers, they cari readily
be recognised in the form of a powder. In order to obtain a
spore-deposit of this nature, one simply takes a pileus, from which
FiG. 31. Spore-deposit produced in about twenty hours from a pileus of
Lepiota rachodes. (The central parts of some of the gills were in contact
with the paper: hence slight disturbances to the regularity of the
deposit.) Natural size.
the stipe has been removed, and places it upon a sheet of paper.
On this the falling spores rapidly accumulate. Owing to their
pronounced adhesiveness, they cling to one another and to any sur-
face with which they come into contact with considerable tenacity.
Spore-deposits cannot therefore be shaken off paper or glass upon
which they have been collected.
RESEARCHES ON FUNGI
In still air, spores, after leaving the hymenial
surfaces, fall vertically downwards at the rate of
about 1-5 mm. per second. 1 If, therefore, one
takes the precaution to eliminate small convec-
tion currents by covering the pilei placed on
paper with small glass vessels, one can produce
a spore print of the gills or hymenial tubes, &c.
Such spore prints are shown in Figs. 31 and
33. In the first one the white spores of Lepiota
rackodes were collected on black paper, whilst in
the second the black spores of Anellaria separ-
ata were collected on white paper. The radiating
spore lines correspond to spaces between the gills.
The rate of accumulation of a spore-deposit
depends on various factors, such as the fungus
species, age of the pileus, temperature, &c. How-
ever, one may often obtain a recognisable spore
print in the short space of fifteen minutes
(Fig. 33, A). As the spores fall continuously,
usually for days together, the deposits become
denser and denser as time goes on (Fig. 33, B
and C). By moving a pileus from one place to
another every hour and thus procuring successive
spore prints, one may readily convince oneself of
the continuity and regularity of spore-emission.
When a pileus is raised above the paper and
spore-deposition takes place under a beaker or
relatively large glass vessel, the spore-deposit no
longer gives a print of the gills but has a cloudy
appearance (Fig. 34, A). The reason for this is
that the air, through which the spores fall, is not
perfectly still but is undergoing slow convection
movements. The spores, therefore, are unable
to fall quite vertically. In Fig. 34, A, is shown
FIG. 32. -Amiiaria sepa- a deposit from a pileus of Anellaria separata
rata. After removal of . \
the stipes, pilei of fruit- raised 2 cm. above the paper. Ihe accumu-
bodies of this species
the spore-deposits shown x Vide infra, Chaps. XV. and XVI.
inFi<rs.33aud34. About
natural size.
SPORE-DEPOSITS
81
lation of the spores took place under a large tumbler during a
night. In Fig. 34, B, one sees that the gills are not perfectly
outlined. In this case the rim of the pileus did not quite
touch the paper all round. The pileus was exposed on a table,
FiU. 33. Spore-deposits from a pileus of Andlaria separata. A pro-
duced in fifteen minutes, B in one hour, and C in six hours.
Photographed natural size.
and therefore affected by convection currents slowly sweeping
beneath it. The result of this was a slight displacement of the
falling spores. In Fig. 34, C, there is shown a deposit made under
a tumbler in the course of four hours from a perfect pileus, the
FlG. 34. Spore-deposits from three pilei of Andlaria separata showing the
effect of convection currents. Explanation in the text. Photographed
natural size.
rim of which was in contact with the paper throughout. Here
the spores fell vertically downwards, and have therefore given an
excellent print of the gills. If one allows spores to fall from
small pieces of pilei placed in specially constructed chambers,
82 RESEARCHES ON FUNGI
designed to reduce convection currents to the least possible
minimum (Fig. 58, p. 167, and Fig. 62, p. 182), spore prints of the
gills can be obtained when the gills are 2-10 cm. above the
collecting surfaces.
It seemed of interest to determine the number of spores liberated
from a few typical fruit-bodies. It has often been stated that
Mushrooms, &c., produce spores by the million. That this is no
exaggeration will be clear from an account of an investigation into
the number of spores produced by fruit-bodies of Psalliota cam-
pestris, Coprinus comatus, Polyporus squamosus, and Deedalia
confragosa.
Psalliota campestris. Fruit-bodies just about to liberate their
spores were obtained from a field. The stipe of one specimen was
cut off, and its pileus, which had a diameter of 8 cm., was placed
in contact with a sheet of white paper. A suitable covering was
used to keep off air-currents. In two days the discharge of spores
appeared to be completed.
The paper containing the spores was placed in 100 cc. of distilled
water, and the whole stirred vigorously until the spores had been
washed off the paper and spread evenly through the fluid. A
Leitz-Wetzlar counting apparatus was then employed and the
number of spores which settled on the squares carefully counted.
As a result of a number of trials, it was calculated that the spore-
deposit represented approximately 1,800,000,000 spores. Since all
these spores fell within forty-eight hours, we must conclude that
on the average about 40,000,000 fell during each hour of the
spore-fall period.
Coprinus comatus. In calculating the number of spores in this
species, a more direct method was employed than that described
above. A gill of Coprimes comatus can easily be split down its
median plane. If, by taking advantage of this fact, one obtains
half a gill and then places it in a closed compressor cell so that
the hymenium looks upwards, one can easily observe the basidia
and spores with the microscope. They form a very regular and
striking pattern (Plate III., Fig. 15). With the aid of a drawing
apparatus, it was found that the number of basidia on O'Ol of a
square millimetre was 34, where the spores were ripening. As
THE NUMBER OF SPORES 83
each basidium bears four spores, it was calculated that the number
of spores on 1 sq. mm. was 13,600.
The fruit-body used for this investigation was a large one (cf.
Plate I., Fig. 1). The pileus was 12 cm. high and possessed 214
gills. Each gill had an area of hymenial surface on its two sides
of 1800 mm. A simple calculation, therefore, showed that each
gill had produced about 24,480,000 spores, and that the number of
spores for the whole fruit-body amounted to the enormous approxi-
mate total of 5,240,000,000. 1 The period of spore-discharge for
large fruit-bodies of Coprinus comatus was found, by making field
observations, to last about forty-eight hours. On the average,
therefore, the fruit-body investigated would have shed 100,000,000
spores each hour of spore-fall.
In the Coprini it is very easy to count the basidia on the
gills, for adjacent basidia on any small part of a gill are practi-
cally in exactly the same state of development, and are set at
regular intervals among the paraphyses. For other Agaricinese,
e.g. Psalliota campestris, this method does not succeed owing to
the fact that adjacent basidia at any one time are in the most
diverse stages of development.
Polyporus squamosus. A fresh fruit-body, which had just
reached maturity, was removed from a tree and placed with its
spores downwards upon a piece of smooth brown paper. Upon
this, after falling down the hymenial tubes, the spores gradually
accumulated in small white heaps (Plate IV., Fig. 27). A square
centimetre of the paper, on which were twenty-six heaps of spores,
deposited from as many tubes, was then carefully cut out and
stirred up with 25 cc. of water. The number of spores in five
drops of the mixture was then counted with the Leitz-Wetzlar
apparatus and, from the data thus obtained, it was calculated that
the number of spores which had been deposited on the square
centimetre of paper was 44,450,000. On the average, then, each
of the twenty-six tubes had produced 1,700,000 spores.
As a control to the above calculation, an estimate was made
1 The average length of the spores in one fruit-body was found to be 12*55 /*.
Placed end to end, therefore, they would stretch through a distance of forty-one
miles !
84 RESEARCHES ON FUNGI
of the number of spores deposited from a single tube of the fruit-
body. It was quite easy to cut out a piece of paper bearing a
heap of spores of the same size as before. This was then stirred
up with 5 cc. of water. As a result of five readings with the
counting apparatus, the number of spores was found to be
1,770,000, which is unexpectedly near the figure indirectly obtained
in the previous calculation. Since the whole fruit-body was some
250 sq. cm. in area, the total number of spores produced by it
FlG. 35. Polyporua squamosus. Two fruit-bodies grown on a log in an
experimental greenhouse. (The early stages of their development are
given in Plate V., Figs. 31-34.) A considerable part of the spores has
settled upon the log, giving it a white appearance. The S was made
in the spore-deposit by rubbing with a finger. About natural size.
would be about the magnitude of 11,000,000,000. The fruit-body
in question, however, was only one of a group of about ten upon
the same tree. The number of spores produced by a single
Polyporus squamosus plant growing in a single tree in the course
of a year, therefore, may exceed 50,000,000,000, and probably in
some instances be not less than 100,000,000,000.
Daedalea confragosa. A fruit-body, about 2 square inches
in area, on being revived, 1 was observed to shed a remarkably
1 Vide infra, Chap. IX.
THE NUMBER OF SPORES 85
dense cloud of spores. These were collected in beakers and then
counted. The results given in the Table indicate that the spores
were liberated most rapidly during the first twelve hours, and that
subsequently the rate of discharge gradually declined. After the
first week, spores continued to fall for about three days longer,
but they were evidently comparatively few in number and formed
but a very thin spore-deposit. Their number was not estimated
with the counting apparatus. The total output of spores in the
laboratory may be taken as very nearly three-quarters of a billion.
Area of Fruit-body approximately 2 Square Inches.
Time.
Number of Spores.
Average Number of
Spores falling
each Hour.
First 12-5 hours.
Next 24 hours .
Next 131-5 hours
112,300,000
140,000,000
429,900,000
9,000,000
5,500,000
330,000
Totals : One week
682,200,000
406,000
It may be of interest, for the sake of comparison with the
Hymenomycetes, to mention the results of a determination of the
number of spores produced by two fungi belonging to other groups
of Basidiomycetes. As an average of ten trials with the counting
apparatus, the number of spores contained within a single smut-
ball of Tilletia caries, developed on Wheat, was found to be
12,125,000. The Mushroom mentioned above, therefore, produced
as many spores as one hundred smut-balls. But numerous as
are the reproductive bodies of a Mushroom, a Coprinus comatus,
or a Polyporus squamosus, they pale into insignificance compared
with those produced by Lycoperdon bovista, Linn. (L. giganteum,
Hussey), the Giant Puff-ball. A large, dry fruit-body of this fungus,
collected by Dr. Wright Wilson and given to the University of
Birmingham, was found to be 40 cm. long, 28 cm. broad, and
20 cm. high. Its weight was 232 grams. The peridium was
removed in one place and O'l gram of the internal, intact gleba
carefully taken out with forceps and weighed. To this small
portion of the fruit-body 250 cc. of methylated spirit were added.
86 RESEARCHES ON FUNGI
Upon being stirred, the spores became evenly scattered in the
fluid. With the counting apparatus, as an average of several
trials, the O'l gram of the fruit-body was calculated to contain
3,245,000,000 spores. The whole fruit-body, therefore, was calcu-
lated to contain 7,500,000,000,000 spores. The fruit-body had a
small sterile base and a very thin, although imperfect, peridium,
but a small part of the gleba had been lost by accident. Taking
these factors into account, it seems fairly safe to state that the
puff-ball produced about 7,000,000,000,000 spores, or as many as
would be liberated by about 4000 good-sized Mushrooms. Pro-
bably a large Giant Puff-ball which, it is said, may sometimes
almost attain the dimensions of a sheep, is the most prolific
organism living on our planet.
The foregoing figures will give some idea of the extraordinary
activity of a large hymenomycetous fruit-body in producing and
liberating spores. It is safe to say that a large Mushroom,
Coprinus comatus or Polyporus squamosus, liberates at least a
million spores a minute, and keeps up this enormous rate of
discharge for several hours or days.
Since it may be assumed that the number of fruit-bodies of
any given species remains fairly constant from year to year, from
the foregoing figures we can obtain a rough estimate for the
rate of elimination of the spores or young plants by death. If
from the spores of a Mushroom of Psalliota campestris only one
Mushroom were eventually produced on the average, then, in
accordance with the figures obtained, it could be stated that
only one spore in about 1,800,000,000 ever manages to develop
into a mature plant. However, it must be remembered that
each spore may produce a wide-spreading mycelium or spawn,
and that this may give rise to a number of fruit-bodies. Doubt-
less also, in nature, the spawn is perennial and often lives for
several years in turf, &c., so that a plant which has arisen from
a single spore must often produce a crop of Mushrooms
annually. If, in consideration of these facts, we assume that,
when a plant succeeds in producing fruit-bodies at all, it
produces altogether on the average ten of them, it may be
estimated that only one spore out of about 20,000,000,000 spores
THE NUMBER OF SPORES 87
ever succeeds in producing a Mushroom plant capable of repro-
duction.
Since a single large Coprinus comatus fruit-body has been
shown to produce about 5,000,000,000 spores, and since the fruit-
bodies often occur in dense clusters together, and further, since
the mycelium in turf is possibly perennial, it seems probable that
successful spores do not number more than one in 20,000,000,000
in this case also. This may well be an under-estiinate. For the
perennial Polyporus squamosus, which produces fruit-bodies from
the same tree, often year after year for several years, it has been
shown that in one case about 100,000,000,000 spores were produced
from the fruit-bodies of one plant in a single year. Since making
this calculation, I have found that large fruit-bodies of Polyporus
squamosus shed their spores continuously for a period of two or
three weeks. When collecting the spores on the brown paper
for the purpose of estimating their number, the fruit-body was
only allowed to remain in position for about two or three days,
for I then thought that spore-liberation would be at an end.
Hence it seems that I have rather under-estimated than over-
estimated the number of spores produced. Taking this into
consideration, and also the perennial character of the plants,
each of which may penetrate through a tree trunk and produce
clumps of fruit-bodies upon it in various places, it seems to
me that for every spore which succeeds in developing into a
mature plant producing reproductive bodies, something like
1,000,000,000,000 spores are wasted. How slight must be the
chances for any given spore of Polyporus squamosus finding a
suitable substratum for successful development!
Of thirteen kinds of fish investigated by F. W. Fulton, 1 the
ling proved to be by far the most prolific in producing eggs. A
large specimen of this species, 61 inches long and weighing 54 Ibs.,
was found to possess a roe containing 28,361,000 eggs. Doubtless
this represented one year's output in spawn. Supposing that
the probable length of life of a spawn-producing ling is as much
as twenty years, the individual under discussion might altogether
1 " The Comparative Fecundity of Sea Fishes," Ninth Ann. Rep. Fishery Board
for Scotland, 1890. Quoted from Cunningham's Marketable Marine Fishes, 1896.
88 RESEARCHES ON FUNGI
have liberated some 500.000,000 eggs. Of course, only a fraction
of these would have been fertilised and rendered capable of
developing into adult ling. We have seen that a single fruit-
body of Psalliota campestris produced 1,800,000,000 spores, one
of Coprinus comatus 5,000,000,000, and one of Polyporus squa-
inosus 11,000,000,000, and that each fungus plant has a perennial
existence and may produce several fruit-bodies each year. Hence,
we may conclude that these fungi are vastly more prolific in
the production of cells capable of reproducing their species than
even the most prolific kind of fish. The danger of going astray
and dying of starvation or other accident appears, therefore, to
be even greater in the case of a fungus spore, when entrusted to
the sportive winds, than in that of a fish's egg when set free in
sea-water and left to the mercy of its currents.
Bower * has calculated that the output of spores of a strong plant
of Nephrodium Filix-mas in a single season approaches 50,000,000.
On the other hand, as we have seen, a single large fruit- body of
Polyporus squamosus produces at least 10,000,000,000 spores. We
may conclude, therefore, that the fungus is vastly more prolific than
the fern.
1 F. O. Bower, The Origin of a Land Flora, London, 1908, p. 23.
CHAPTER VI
MACROSCOPIC OBSERVATIONS ON THE FALL OF SPORES OF
POLYPORUS SQUAMOSUS
FROM the foregoing chapter it is clear that enormous numbers of
spores fall continuously during the spore-fall period of a large
hymenomycetous fruit - body. Nevertheless, the spores are so
minute that, as a rule, one cannot observe the spore-clouds with
the unaided eyes. If it were not for the exact investigation into
the matter, it would be difficult to believe, when one holds up a
large ripe Mushroom, that, before one's very eyes but yet unseen,
a million spores fall from the gills each minute. However, a
visible spore-discharge has occasionally been observed as a rare
phenomenon. Thus Hoffman 1 has recorded having seen spore-
clouds leaving the under surface of Polyporus destructor, whilst
Hammer 2 has more recently observed tiny wreaths of spores
ascending to a height of 2 or 3 feet from a fruit - body of
Pleurotus ostreatus placed upon a table. Hermann von Schrenk 3
states that from a fruit-body of Polyporus Schweinitzii, " the
spores came oft' at intervals as if they were being discharged
by some force acting within the tubes." It may be remarked
that, from numerous observations of my own made by the beam-
of-light and other methods 4 on various species of Polyporese,
there seems to me to be no doubt that the spores which von
Schrenk observed were falling continuously and regularly by their
own weight, and that the intermittent clouds were caused by
tiny, irregular air-currents which swept the spores along beneath
1 Hoffman, Jahrb.fur wiss. Pot., Bd. II., 1860.
2 Hammer, "A Note on the Discharge of Spores of Pleurotus ostreatit*" Torreya,
V., 1905, p. 146.
3 H. von Schrenk, "Some Diseases of New 'England Conifers," Bull 25, U.S.
Dep. of Agric., 1900, p. 22.
* Vide infra, Chap. VII.
90 RESEARCHES ON FUNGI
the fruit-body at intervals in much the same manner as steam is
swept by air-currents from the surface of hot water.
In the month of July, 1905, I was fortunately enabled to make
direct observations upon the falling of the spores from the fruit-
bodies of Polyporus squamosus. My attention was first called to
this matter by Mr. C. Lowe, the laboratory attendant. A log,
producing fruit-bodies of the fungus, had been placed in the
experimental greenhouse at the Birmingham Botanical Gardens.
Going into the greenhouse one morning, it appeared to Mr. Lowe
that some one had been smoking there. On looking round he
observed that the " smoke " was coming from the underside of
a freshly -grown fruit-body which was some 10 inches in diameter.
From that morning onward until the thirteenth day, every time
the greenhouse was entered (morning, afternoon, and as late as
nine o'clock in the evening), the clouds of spores were observed
coming off from the fungus. On the thirteenth day the clouds
were very feeble at nine o'clock in the morning and ceased to be
visible about an hour later. Black paper was then placed under
the fruit-body and on this the white spores collected. By changing
the paper at intervals, I was able to satisfy myself that the spores
continued to fall in fairly large quantities for three days more. The
black paper was whitened by the spores, but only very feebly on
the last day. Altogether, therefore, these observations proved that
the spores had been falling continuously for sixteen days.
The clouds of spores, which were watched by the hour against
a black background, resembled the steam coming off a cup of tea
or the finest tobacco smoke. The wreaths and curls of spores
appeared to originate in eddies made by air-currents in passing
over the hymenial surface. Tapping the fruit-body so as to make
it tremble did not appreciably increase or diminish the clouds
of spores. The wreaths could be made by artificial air-currents
produced by movements of the hand near the fruit-body. Some
of the wreaths could still be seen after they had floated away to
a distance of two yards. The clouds were distinctly visible on a
black background when they were observed at a distance of ten
yards from the fruit-body.
The log upon which the fruit-body was growing was watered
MACROSCOPIC OBSERVATIONS 91
from time to time, but the air of the greenhouse was dry. It
seemed of interest to find out whether or not moist air causes a
diminution in the rate of spore-fall. Accordingly, the log was
removed to the Hymenophyllum house after this had been so
well syringed that its warm atmosphere appeared to be saturated
with moisture. The spores, however, continued to fall for two
hours quite as rapidly as in the dry greenhouse. Wreaths and
curls of spores floated slowly away from the fruit-body. The
log was then taken back to its former dry situation, where the
visible fall of spores went on unabated. Ordinary variations in
FlG. 36. Spores leaving a fruit-body of Polyporus squamosus and being carried
away by slow air movements. natural size.
the hygroscopic state of the atmosphere, therefore, do not appear
to affect appreciably the fall of the spores.
Some very young fruit-bodies which just showed the earliest
indications of the development of hymenial tubes were found
growing upon a log of wood in the open. The log was immediately
removed and placed in a dark room. Under these conditions
the hymenial tubes developed in a normal manner (cf. Figs. 5, 6,
and 7, pp. 29, 32, and 33), and on the fourth day abundant spore-
clouds were produced. These continued to fall for eleven days,
at the end of which time the fruit-body had begun to wither.
The production and liberation of spores, therefore, appear to be
carried on quite independently of light.
The hymenial tubes begin their development as saucer-shaped
structures on the underside of the pileus. The walls of the tubes,
which are positively geotropic, then grow vertically downwards
for some days. By elongating in this manner, the tubes, although
often shorter, may attain a length of a centimetre (Fig. 7, p. 33).
92 RESEARCHES ON FUNGI
Their polygonal pores are shown in Fig. 6, p. 32. By making
suitable sections and using the microscope, it was found that ripe
spores were being discharged when the tubes on a young fruit-
body were only 1 mm. long. These observations lead me to suppose
that, in the case of the fruit-body for which it was found that the
spore-fall period lasted sixteen days, spore-emission had already
been in process for about a week before the spore-clouds were dis-
covered. Probably, therefore, in that instance the total spore-fall
period extended over about three weeks.
By placing black paper beneath a ripe fruit-body for the purpose
of collecting the spores, it may easily be proved that each tube
emits spores continuously for several days. It may also be shown
that, except for a small zone about 1 mm. high at the mouth where
no spores are developed, every part of a tube produces spores.
A very large fruit-body, '2 ft. 2 in. across, was gathered from a
tree and a vertical section made through the pileus (Fig. 7, p. 33).
The section was placed on black paper. In twenty-four hours each
half-tube had produced a spore-deposit. The tubes were on the
average about 9 mm. long, and the spore-deposits, which were of
an even character, 8 mm. long, spores not having been produced
by a zone round the tube mouths. A photographic reproduction
of the deposits is shown in Plate IV., Fig. 28 ; and Plate IV., Fig. 27,
gives a spore-deposit collected from the mouths of hymenial tubes
disposed on a square inch of the pileus. We may draw the con-
clusion from these macroscopic observations that each hymenial
tube during its development liberates spores for several days from
every part of its spore-producing surface.
The chief reason why one can see the clouds of spores so easily
in Polyporus squamosus is that the spores come off from the fruit-
bodies in such vast numbers. In one case, as already stated, a
single square centimetre of a fruit-body produced at the very least
44,450,000 spores in two or three days. A spore-cloud resembles
a steam cloud : the whole becomes visible owing to the vast number
of the microscopic constituent particles. The spores, too, are com-
paratively large (14'6x5*13 /A) and also colourless. They absorb
very little of the light falling upon them, but reflect and refract
most of it, so that they glisten. Like all other particles, the spores
MACROSCOPIC OBSERVATIONS 93
fall by their own weight in the air. Since the rate of fall in quite
still air is uniform and only about 1 min. per second, 1 whilst air-
currents and convection currents beneath the fruit-bodies have
proportionately a much greater speed, which amounts, even in a
quiet greenhouse, to several feet per minute, it is not astonishing
that the spore-clouds appear to float away from the fruit-bodies
as if they were not sinking at all.
1 Vide infra, Chaps. XV. and XVI.
CHAPTER VII
THE DEMONSTRATION OF THE FALL OF SPORES BY MEANS
OF A BEAM OF LIGHT
AFTER I had made the observations upon Polyporus squamosus
which have just been described, it occurred to me that it might
be possible to see the clouds of spores falling from any hymeno-
mycetous fungus with the aid of a sufficiently strong beam of
light. Accordingly, a large Horse-mushroom (Psalliota arvensis)
was obtained and placed as a cap on an open glass box. The light
from an electric arc was allowed to pass through a small hole in
a dark screen, and the rays were then collected and turned into
a strong parallel beam by means of a biconvex lens. The beam
was then directed so that it passed through the glass box. At once
a very striking and remarkable result made itself apparent. On
looking at the beam of light in the box, one could see the spores
floating in the air in countless thousands. It seemed as if, in
miniature, a heavy brown-flaked snow-storm was taking place.
Curls and wreaths of spores, formed by convection currents, were
constantly proceeding from the gills, and the air in the box quickly
became densely laden with spores. In the course of a few minutes
the density of the spore-cloud in the box became constant. At this
stage, doubtless, just as many spores settled on the bottom of the
box as were given off at the top by the Mushroom gills. The
spores were not to be seen merely as clouds. One could clearly
perceive any individual spore floating in the light, and follow its
course for some distance. 1 It has thus fallen to my lot, by using
a very simple method, to be the first actually to observe the
1 On the same principle that one can see a star, although it has no appreciable
disc, or a spider's web in strong sunlight at a distance of several yards. One does
not perceive the dimensions and shape of a spore owing to the insufficient resolv-
ing power of the eye. One is simply aware that it sends out light.
THE BEAM-OF-LIGHT METHOD 95
fascinating spectacle of millions of spores leaving the gills of a
Mushroom.
It must not be supposed that the ordinary dust particles, which
are always present in the air in countless numbers, were mistaken
for spores. With a concentrated beam of light it is very easy to
see the dust particles. In my laboratory they are roughly of two
classes: the coarser ones are comparatively rare and consist of
fibrous matter, &c., whilst the finer ones are extraordinarily
numerous and doubtless of the most varied origin. The coarser
particles alone can be mistaken for spores, but a very little experience
is sufficient to prevent confusion. These dust particles never
occur in the form of wreaths or curls, and only occasionally float
into the beam of light. Further, they are irregular in shape and
rarely affect the light in the same manner as a spore. The finer
particles are distinctly smaller than spores, never so regular in
size, and more numerous. They are also somewhat difficult to
see individually, for they do not glisten in the light nearly so
brightly as spores. It is evident, therefore, that spores and ordinary
dust particles can be distinguished in a beam of light with great
ease.
After finding that the beam-of-light method could be applied
with so much success to a Mushroom, I made general use of it in
investigating the spore-fall of a large number of other species. It
has proved of great service in determining whether or not spore-
discharge was taking place in any particular fruit-body, in finding
out the length of the spore-fall period, and in studying the effect of
various external conditions upon spore-liberation.
It may be stated quite generally that, whenever spores are falling
from a fruit-body, they can be observed with the unaided eye in a
strong beam of light. So far as my experience goes, there are no
species of Hyrnenomycetes of which the spores are too small to be
seen in this macroscopic manner. Even a very slight discharge from
a fruit-body may be detected. Sufficient evidence of its occurrence
is provided by a dozen spores streaming through a beam.
It was found convenient in my own department to carry out
observations with the beam-of-light method in the following manner.
The lecture-theatre lantern, provided with an electric arc, was set
96 RESEARCHES ON FUNGI
upon a suitable wooden stand, so that the front lens was about 5
feet above the ground. To the lens was attached a black cap, in the
middle of which a round aperture, one and a half inches in diameter,
had been made. A bull's-eye condenser a plano-convex lens
mounted upon a stand adjustable for any position, such as is com-
monly used for illuminating opaque objects was then placed in
front of, and close against, the aperture so that, when the arc was
turned on, the condenser formed a concentrated beam of light. The
chamber into which the spores were liberated usually consisted of
a beaker, 6 inches high and 4 in diameter, closed above by a
circular glass plate (Fig. 37). A piece of sheet cork was fixed on to
the middle of one side of the plate by means of sealing-wax. A
living fruit-body, to be tested, was pinned on to the cork so that,
when the plate was placed on the beaker, the fruit-body had its normal
orientation, the hymenial side looking downwards. The beaker was
then set close in front of the condenser in the beam of light.
If a fruit-body is active, a stream of spores can be detected
coming from it within a few seconds after it has been placed in
position above the beam. The stream is carried slowly round and
round in the beaker by convection currents. It gradually breaks up
so that in a few minutes the spores are well scattered (Fig. 37). A
maximum density of spores is soon attained. At this stage as many
spores settle as are liberated. If one directs the beam of light so
that it passes through the air just beneath the gills or hymenial
tubes, &c., one can observe the spores slowly emerging into view.
They are then simply falling by their own weight, at the rate, in
many species, of 1-2 mm. per second. 1 Convection currents sweep
the spores, as they emerge from the gills, hymenial tubes, &c., slowly
in one direction, and it is thus that a steady stream of spores arises.
The density of the stream remains very regular for hours or even
days. There is no evidence whatever that the spores are discharged
intermittently. The most remarkable thing about the liberation of
the spores is just its constancy for considerable periods of time. An
unbroken stream of spores was observed to be emitted from the fruit-
bodies of species of Polystictus, Lenzites, Schizophyllum, Stereum,
&c., for days and in some cases for more than two weeks.
1 Vide infra, Chaps. XV. and XVI.
THE BEAM-OF-LIGHT METHOD
97
The spores of white-spored species stand out in the beam of light
as distinct white particles, whilst the purple-brown ones of the
H'. : 4
Pt
FIG. 37. Diagram illustrating the discharge of spores from a
fruit-body of Polystictus versicolor as seen by the beam-of-
light method. The fruit-body is pinned in its natural
position to a piece of cork attached to a circular glass
cover placed upon a beaker. A stream of spores is carried
round within the beaker very slowly by convection cur-
rents and gradually breaks up so that the spores become
scattered fairly uniformly. Reduced to about .
Mushroom and the black ones of Coprini present brownish and dull
metallic appearances respectively.
It has been determined, by methods to be explained subsequently,
that very small spores, such as those of Collybia dryopkila, in still
air fall at the rate of about 0*5 mm. per second, and that the very
largest, such as those of Coprinus plicatilis, fall at the rate of about
98 RESEARCHES ON FUNGI
5 mm. per second. Mushroom spores fall at a speed of about 1 mm.
per second. It is not surprising, therefore, that convection currents
carry the spores round in the beakers for a considerable time before
they settle down, and that the spores become spread fairly uniformly
in the air of any small closed chamber. In one experiment I placed
a piece of a Mushroom (Psalliota campestris) at the top of one end of
a box which was 107 cm. long, 7 mm. wide, and 13 cm. high, and
which was illuminated with a parallel beam of light sent through it
lengthwise. The spores were gradually scattered in the enclosed air.
Some were even carried to within a few centimetres of the end of the
box opposite to that in which the fungus had been placed. This
observation shows that very small convection currents are capable of
carrying the spores over a metre from a fruit-body in the lateral
direction.
From observations which I have made upon the fall of spores in
glass chambers of various sizes, it seems that convection currents
are such that the spores in a sufficiently large chamber (large
beakers, &c.) tend to spread themselves uniformly within its con-
tained air, so that equal numbers of them come to occupy each
available unit of space. Richard Falck l observed the spore-deposits
made by fruit-bodies placed in chambers provided with vertical
series of small paper shelves, and he found that the shelves, even
when they had been placed one above the other at short intervals,
became equally covered with spore-dust. My own observations upon
falling spores, made by the beam-of-light method, have enabled me
to explain Falck's results in the following manner : Convection
currents are usually of such strength in the chambers that the
spores are moved about by them so that equal numbers come to
occupy each unit of space. As a result of this, there is the same
number of spores in the layer of air immediately over each shelf.
As the spores are falling by their own weight at the rate of about
1 mm. per second, 2 a certain number settle each second. Since the
conditions for the settling down of spores over each shelf are
1 R. Falck, " Die Sporenverbreitung bei den Basidiomyceten," Beitrage zur
Biologic der Pflanzen, Bd. IX., 1904.
2 The rate varies according to the species; c/. the Table of velocities in
Chap. XV.
THE BEAM-OF-LIGHT METHOD 99
approximately the same, the shelves must eventually all become
uniformly covered with a spore-deposit.
Falck has also called attention to the fact that, when the pilei of
certain fungi are suspended in a glass chamber, one sometimes
obtains curious and fantastic spore-deposits on paper placed at the
bottom of the vessel. These irregular spore-deposits are in my
opinion entirely due to the nature of the convection currents in the
glass vessels. Observations with the beam-of-light method have
taught me that, when the velocities of the convection currents are
high compared with the constant rate of fall of the spores due to
gravity, the spores become evenly distributed in each unit of space
in^the chamber, and that a uniform spore-deposit collects in con-
sequence upon the bottom of the chamber, shelves, &c. If, how-
ever, the spores, such as those of various species of Coprinus, are
large and heavy, and fall at the rate of several millimetres per
second, and if, in addition, the convection currents are not strong
compared with this rate of fall, then we have the conditions
for the formation of a localised and irregular spore-deposit at
the bottom of the chamber. In general it may be stated that
the appearance of any spore-deposit is decided partly by the
speed and nature of the movements of the air through which
the spores have fallen, and partly by the rate of fall of the spores
themselves.
The pileus of a small Coprinus fruit-body which came up on
horse dung and was liberating its spores, was suspended at the top
of a closed glass chamber which was about 6 inches high, 4 inches
wide, and covered below with white paper. The chamber was placed
in front of the condensing lens of the lantern. It was observed that
a black spore-deposit was accumulating on the white paper along one
side of the base of the chamber. After about an hour it was assumed
that the chamber had taken on the room temperature. The arc-
light was suddenly turned on, and with the beam a stream of spores
could be seen leaving the gills, falling obliquely at a rate of several
millimetres per second, and settling where the spore-deposit had been
accumulating. Owing to the sides of the vessel becoming warmed
by heat accompanying the beam of light, new and marked convection
currents were soon formed. The result was that the stream of spores
ioo RESEARCHES ON FUNGI
became deflected into a new path, and the spores became scattered
fairly regularly. In quite still air in very small chambers, Coprinus
spores fall quite vertically. 1 These observations seem to me to
warrant the belief that the localised and irregular spore-deposit
formed by the Coprinus in the first instance was due to convection
currents which kept circulating in a constant path, thereby deflecting
the rapidly falling stream of spores out of the vertical toward one
side of the jar. It is scarcely necessary to discuss how regular
convection currents might arise in the closed system which was
employed, but it may be pointed out that the living and actively
respiring Coprinus pileus might well be responsible for them.
Falck arranged tiers of circular paper discs, one above the other,
in a tall cylindrical glass chamber where a pileus was liberating
its spores. Under these conditions he often obtained very curious
radiating spore-deposits on each disc. Here, again, the assumption
that convection currents taking regular paths existed in the
chamber, seems to me quite sufficient to give a basis for an ex-
planation of the results. As one may readily observe by means
of the beam-of-light method, the spores are carried away from
the underside of the pileus in the form of a comparatively thin,
dense, and continuous stream. The stream which reveals the
presence of convection currents, doubtless, would be carried along
slowly, first over one surface, then over another, dividing here
owing to this obstacle, and turning back there owing to another,
until finally it would be broken up. Where on any surface a
dense trail of spores has accumulated, it may be assumed that
the spore stream took a regular path just above. If the convection
currents are only fairly constant in their directions, then owing to
the fact that the spores in the first instance are swept away from
the pileus in the form of a stream, fantastic spore-patterns seem to
be just what should be expected under the conditions provided
by Falck's experiments.
In concluding my remarks in this chapter, I wish to recommend
the demonstration of spore-fall by the beam-of-light method to
all those who give lectures or laboratory courses which include a
treatment of the fruit-bodies of Hymenomycetes. It is difficult
1 Vide infra, Chap. XV.
THE BEAM-OF-LIGHT METHOD 101
for a student to realise that millions of spores are falling each
hour from a ripe Mushroom before his or her very eyes, and yet
unseen. A single demonstration of the kind that I have described
is likely to impress the fact indelibly on the memory. The demon-
stration can be carried out on any day in the year, even in the
depth of winter. Subsequently, it will be shown that there are
many species belonging to the genera Lenzites, Polystictus, &c.,
which can be kept dry in bottles for months or even years, and
which yet shed spores again for days after they have been revived
by being placed for about six hours under moist conditions. A
stock of such fruit-bodies may be kept in the laboratory, and
revived at any time with great ease and certainty by placing wet
cotton-wool on the pilei. Instead of a strong artificial beam of
light, sunlight, let through a slit in a dark room, is equally effective
for the purpose of illumination.
CHAPTER VIII
THE SPORE-FALL PERIOD
THE spores of a hymenomycetous fruit-body, under favourable
conditions, are liberated continuously at a fairly constant rate.
They are never all discharged simultaneously or set free in inter-
mittent showers. The falling spores may be compared to raindrops
steadily falling from the clouds on a wet day. The process of
spore-discharge often requires a considerable period of time. This
may be conveniently called the spore-fall period.
In any given fruit-body, the spore-fall period varies in length
according to the rate of development of the spores. This depends
on internal organisation and also upon external conditions, more
particularly of temperature. For many corky or leathery fruit-
bodies, such as those of Lenzites, Polys tictus, Stereum, &c.,
which readily become dried up in a dry atmosphere and
quickly absorb free water through the upper surfaces of their
pilei, rainfall and dew formation are distinctly favourable to
the discharge of spores, whilst drought must often temporarily
interrupt it.
It has already been recorded 1 that a large specimen of Poly-
porus squamosus, growing on a log, was observed to shed its spores
continuously for sixteen days. Reasons were also given for sup-
posing that in this case the spore-fall period must have extended
over at least three weeks.
The length of the spore-fall period was determined for a number
of xerophytic fruit-bodies by means of the beam-of-light method.
The fruit-bodies which had been detached from the substrata and
allowed to dry up were revived in a damp-chamber, suspended
in beakers, and examined usually several times a day with a beam
from an arc-light. The beakers were kept in a well-heated labora-
1 Chap. VI.
THE SPORE-FALL PERIOD 103
tory. Moisture was supplied to each fruit-body by means of wet
cotton wool placed on the upper surface.
An apparently full-sized fruit-body of Schizophyllum commune,
less than a square inch in area, shed its spores for sixteen days
continuously. The density of the spore-stream leaving the gills
seemed to remain almost constant from a few hours after its
formation onwards, until about three days before the end of the
spore-fall period, when it began to grow distinctly feebler.
A small fruit-body of Polystictus versicolor shed spores for
sixteen days, and one of P. hirsutus for five days. A large
specimen of Lenzites betulina gave a copious shower for ten days.
A number of other fruit-bodies, such as those of Stereum hirsutum,
S. purpureum, Dsedalea unicolor, Merulius corium, &c., were seen
to discharge their spores for several days. A complete investi-
gation into the spore-fall period in all these species, doubtless,
would add much to its length. In order to carry it out, it would
be necessary to examine a fruit-body growing upon its substratum
from the time it begins to develop its hymenium onwards. It
has already been found that a very young fruit-body of Polystictus
hirsutus, grown in the laboratory on a stick, began to shed a few
spores when its hymenial tubes had only attained the size of
hemispherical depressions. From this observation, and also from
the fact that both small and large fruit-bodies of Schizophyllum,
Lenzites, Polystictus, &c., liberate spores when kept moist, it seems
probable that spore-fall takes place in species belonging to these
genera in a manner similar to that exhibited by Polyporus squamosus,
i.e. the discharge of spores begins soon after the fruit-bodies have
expanded horizontally, when the hymenium begins its development,
and continues until the pilei Have grown to their full extent. This
may be in some cases a matter of days, in others certainly of weeks,
or in yet others possibly of months.
For Psalliota campestris and allied fruit-bodies spore-fall does
not begin until the pileus has expanded and the gills have become
more or less horizontally outstretched. By placing paper close
beneath the pilei of some Mushrooms growing on an artificial bed,
and thus collecting the spores, it was found that the spore-fall
period continued for two or three days.
io 4 RESEARCHES ON FUNGI
A fully expanded fruit-body of Pleurotus ulmarius, when
confined in a large beaker in the laboratory, was observed by the
beam-of-light method to shed spores for seventeen days continu-
ously. During the last few days the gills gradually turned mouldy.
Since the fruit-body appeared to be of full size and expansion when
gathered, it seems probable that, had it been left to continue its
existence under natural conditions, its spore-fall period might have
exceeded three weeks.
Coprinus comatus sheds spores from the moment "deliquescence"
begins at the base of the gills until these have disappeared. For
some large specimens, growing in a field under favourable weather
conditions, the spore-fall period was found to last about two days
and two nights. Smaller species of Coprinus, such as C. plicatilis,
shed their spores in a few hours.
The continuous discharge of spores for days or weeks is certainly
a remarkable fact which requires further elucidation from the point
of view of development. It must be remembered in this connection
that adjacent basidia in most fruit-bodies are in very various stages
in regard to the production of spores. The fact that after the spores
on a basidium have attained their full size and final colour, they
remain on the sterigmata but a very short time, seems to show that
they are discharged as soon as ripe. There must be some means by
which a succession of developing basidia on any given part of the
hymenium is provided. Possibly the discharge of spores from one
basidium serves as a stimulus for the development of one or more
neighbouring basidia. It is certain, however, that the process is
beautifully regulated, for thus only could a Polyporus squamosus,
a Lenzites betulina, or a Polystictus versicolor give out millions of
spores in such steady streams for many days without interruption.
CHAPTER IX
DESICCATION OF FRUIT-BODIES A XEROPHYTIC FUNGUS
FLORA THE GENUS SCHIZOPHYLLUM
HITHERTO the retention of vitality by fruit-bodies after desiccation
does not appear to have been thoroughly investigated. In systematic
works on fungi, it is stated that fruit-bodies in the genera Marasmius
and Collybia revive after .being dried up when they obtain access to
moisture, but beyond this general fact nothing further seems to have
found its way into botanical literature. However, probably most
field mycologists have noticed that leathery and corky fruit-bodies
occurring on sticks and logs of wood become freshened up in rainy
weather.
A test for retention of vitality is not afforded by the fact that a
dried fruit-body, when viewed macroscopically, apparently regains its
turgidity on access to moisture, for a number of 'dead fruit-bodies
swell up in this way, e.g. Lenzites betulina. The swelling in this and
many other species is simply due to the expansion of the hyphal
walls. A slow oxydative change going on in a dried fruit-body
would also be an unreliable test for retention of vitality, for Paul
Becquerel 1 has shown that seeds which were killed by heating and
then dried, " respired " more actively than dried seeds still capable of
germination. If, however, when supplied with moisture, a fruit-body
again begins to shed spores, then we have a clear and convincing
proof that it is still living. A fruit-body which has been killed
never sheds any spores. Even when a fruit-body which is actively
discharging spores is placed under the influence of ether vapour, 2
spore-fall ceases immediately. The liberation of spores, therefore, is
an active process, the carrying out of which may be taken as sure
evidence that the fungus concerned is still living.
1 P. Becquerel, " Sur la nature de la vie latente des grains et sur les veritable
charactores de la vie," Comptes Rendus, T. 143, 1906, p. 1177.
2 Vide infra, Chap. X.
105
106 RESEARCHES ON FUNGI
Experience has shown that spores which have just been liberated
always have a fresh and turgid appearance when observed in water.
They give one the impression that they are capable of germination.
That spores, newly shed from a fruit-body which previously has been
kept desiccated for a long period, may germinate readily under
suitable conditions, has been proved for the only two species so far
tested, namely, Dtedalea unicolor and Schizophyllum commune. A
fruit-body of the former species was kept dry for three years, and one
of the latter for one year. They both recovered when wet cotton
wool was placed on their upper surfaces. Spores
liberated within ten hours after the fruit-bodies
had been moistened germinated readily within
a further twenty-four hours in hanging drops
of a nutrient medium containing meat extract,
grape-sugar, peptone, and gelatine (Fig. 38).
These observations seem to afford strong evidence
in favour of the view that, whenever spore-emis-
sion is taking place from a fruit-body, the
emitted spores are living.
F were 8 ^ ?ro r m' JvS Xt not ^frequently happens that a desiccated
fruit-bodies, in course fruit-body, separated from its substratum and
of germination after ,, . .,,..
twenty-four hours in a allowed access to water, in addition to liberating
SSltZ: 1' spores also recommences growth. Such growth
Schizophyllum commune. i n species of Polyporefe may lead to a slight
Magnification, 700. J
elongation of the hymenial tubes or even to the
production of very shallow new ones at the edges of the fruit-bodies.
Renewed growth of this kind can easily be detected macroscopically,
and it has been observed in Polyporus rigens, Polystictus hirsutus,
and Glwoporus conchoides. The fruit-bodies in question had been
kept dry for a year before being moistened.
Most succulent fruit-bodies, such as those of species belonging to
the genera Psalliota, Amanita, Coprinus, Boletus, &c., are unable to
survive even partial desiccation. The Marasmii are exceptions to
this rule. Fruit-bodies of Marasmius oreades were gathered from a
" fairy ring " in a field and, when tested in the laboratory, were found
to be freely liberating spores. They were then well dried by means
of hot air. During the drying process the fleshy pileus became quite
DESICCATION OF FRUIT-BODIES
107
stiff and white, and the gills shrivelled up (Fig. 40, A, B, and C).
After the fruit-bodies had been kept in the dried state for twenty-
four hours, free water was allowed to come into contact with the
upper surfaces of the pilei and with the stipes. It was readily
absorbed. The fruit-bodies became swollen, and completely resumed
their normal appearance in the course of a few hours (D and F).
At the end of this time they were actively shedding spores. Thick
spore - deposits collected
beneath the pilei on black
paper (E), and the dis-
charge of spores from the
sterigmata was watched
by means of microsco-
pic sections. Convincing
proof was thus obtained
that the fruit-bodies of
Marasmius oreades, after
complete desiccation, are
capable of reviving on
access to moisture and of
resuming their normal
activities. The retention
of vitality in the dried-up
condition, however, is only
temporary. It was found
by subsequent experi-
ment that fruit - bodies
which had been kept stiff
and hard were still capable of recovery after six weeks but not
after three months.
Fruit-bodies of Marasmius peronatus and of Collybia dryophila
were allowed to dry on a laboratory table. They were then tested at
intervals for revival. The tests showed that recovery was possible
when the desiccated condition had lasted for only a few days, but not
when it was continued for a month.
On hot days in summer and early autumn, one not infrequently
sees shrivelled-up fruit-bodies of Marasmius oreades in " fairy rings "
FIG. 39. Marasmius oreades. To the left a fruit-
body shrivelled up during drought. To the right
a fruit-body which after becoming shrivelled up
was revived under moist conditions and is again
shedding spores. Natural size.
io8
RESEARCHES ON FUNGI
in meadows (Fig. 39). The fruit-bodies are developed during a spell
of wet weather, but, when the air and soil become reduced in
moisture, and especially when the radiation of the sun is intense,
they slowly dry up and cease to shed spores. As soon as rain comes
again, water is quickly reabsorbed through the top of the pileus, and
the spore-liberating function is resumed. There can be no doubt
that the revival of the fruit-bodies of Marasmii after desiccation is
an advantageous adaptation which prevents a great loss of spores.
FlG. 40. Marasmius arcades. A and B, the under surfaces, and C, the upper
surface of the pilei of three fruit-bodies after desiccation. D and F are the
pilei A and C respectively three hours after the commencement of revival by
absorption of water through their upper surfaces. E, a spore-deposit from
the pileus D (A revived). Natural size.
During dry weather in early autumn I have several times gathered
shrivelled-up specimens of Collybia dryophila growing among leaves
in woods. Upon being wetted, the pilei soon became fully expanded
again, and spore-liberation was then actively resumed. It is evident
that the fruit-bodies of Collybia dryophila retain their vitality after
desiccation in just the same manner as those of Marasmius oreades.
As a result of experiments upon a considerable number of typical
species, the names of which will shortly be given in a Table, it seems
A XEROPHYTIC FUNGUS FLORA 109
safe to state that very many, and possibly all, of the small leathery
and corky fruit-bodies of Hymenomycetes which are to be found
developing on fallen logs and sticks in woods, are capable of com-
plete recovery after desiccation. In a number of instances they can
be kept dry for months or even for several years, apparently without
the smallest detriment to their power of liberating spores after
absorbing water once more. Among the species in question one may
mention those belonging to the following genera : Schizophyllum,
Lenzites, Trogia, Dsedalea, Polyporus, Polystictus, Merulius, Phlebia,
Stereum, and Corticium. These fungi must be regarded as xero-
phytes, for their fruit-bodies are capable of withstanding drought
by drying up without any loss of vitality and of reviving again
under moist conditions.
Fruit-bodies of Lenzites, Polystictus, &c., which were required
for testing, were gathered during October and November from
stumps, logs, and sticks in the woods near Winnipeg, and placed
on a table in the laboratory. There the air was very dry, so that
desiccation took place rapidly. A dried fruit-body, still living,
revived when it had been set in a damp-chamber and wet cotton-
wool had been placed on the top of its pileus. It quickly absorbed
the free water, expanded, and soon came to have a fresh appear-
ance. After a few hours spore-liberation was resumed. This was
proved in my first experiments by collecting spore-deposits on paper,
but subsequently this method was discarded and the beam-of-light
method used instead. It has already 1 been made sufficiently clear
that a strong beam of light, directed beneath a fruit-body in a closed
beaker, readily enables one to determine whether or not spore-fall
is taking place.
As a rule, only a very few hours are required for a dried-up
fruit-body to regain its spore-liberating function. A specimen of
Schizophyllum commune, kept dry for six months, recovered in
three hours. Merulius corium and Polystictus versicolor, kept dry
for six months, and Lenzites betulina, kept dry for two years and
six months, all required about four hours to recover. In other cases
it was found that spore-fall usually recommenced within six hours
after the fruit-bodies had been placed under moist conditions. A
1 Chap. VIII.
no RESEARCHES ON FUNGI
fruit-body of Dtedalea unicolor, kept dry for two years and six
months, recovered in about four hours, but another fruit-body of
the same species, kept dry for four years, recovered in about 7*5
hours. This observation indicates that those fruit-bodies which
have been kept longest in the desiccated condition are the slowest
to revive.
All the fruit-bodies tested were found to retain their vitality
for several months, some of them for more than two years, and one,
namely, Diedalea unicolor, for more than four years. Only in a few
species, owing to lack of material old enough, has it been possible
for me to determine within what period death occurs. However,
the investigation seems to indicate that every dried fruit-body
exposed to the air loses its vitality in the course of a few months
or years, just as does a seed. 1 In the Table opposite is given
a list of the fungi which were tested, and also the results of tests
made after various periods of desiccation.
Some well-grown specimens of Lenzites betulina and of Schizo-
phyllwm commune were collected. Doubtless, they had already
shed an abundance of spores before they were gathered. They
were kept dry for a whole year, and then revived in a damp-
chamber, whereupon they shed clouds of spores. Again, by drying,
they were put to rest for another year, and at the end of this second
period of desiccation they were again allowed access to free water.
They revived and shed spores once more. A similar revival was
found to take place even after desiccation for a third year, but an
attempt to revive the fruit-bodies after a fourth year of desiccation
was unsuccessful: the fruit-bodies became discoloured and putrid
without shedding any spores.
Sticks, dead branches, and logs in woods are all liable to become
dried up. When this happens the mosses, lichens, and fungi upon
them must gradually dry up too. It is not surprising, therefore,
that these plants are adapted to withstand temporary desiccation.
1 Paul Becquerel (loc. cit., p. 1178) found that dried seeds of various kinds
placed in pure and dry nitrogen in the dark for a year, did not liberate a trace
of carbon dioxide, and yet germinated subsequently. It will be of interest to
determine whether or not dried fruit-bodies of fungi are also capable of retaining
their vitality without any evidence of respiratory activity. If life may become
latent in dry seeds, it may also do so in dried fruit-bodies.
A XEROPHYTIC FUNGUS FLORA
They survive through periods of drought by drying up and retain-
ing their vitality. The hyraenomycetous stick or log flora is
therefore xerophytic.
While it has now been demonstrated that many of the fruit-
bodies of wood-destroying fungi are able to withstand desiccation
unharmed, the resistance of the mycelium to dry conditions still
requires an experimental investigation. Quite possibly in some
List of Hyinenomycetes with fruit-bodies which can become Desiccated
without losing their Vitality.
Family.
Species.
Recovered after
Desiccation lor
Failed to Recover
after Desiccation for
' Corticium laeve
1 year
Thelephoreae -
Stereum hirsutum
,, purpureum
bicolor
1 year
1 year
1 year 6 months
1 year 6 months
2 years
Hydnese . .
Phlebia pileata
zonata
2 years 8 months
1 year
4 years 4 months
3 years 6 months
Merulius corium
2 years
...
Gloeoporus conchoides
1 year
Dtedalea unicolor
4 years
...
confragosa
1 year
quercina
1 month
5 years
Polyporese . -
Polyporus conchifer
4 months
5 months
rigens
2 years
carneus
2 years
...
Polystictus versicolor
2 years
4 years
hirsutus 3 years
...
pergamenus 1 year
Trogia crispa 4 months
1 year
Schizophyllum commune 2 years
16 years
Lenzites betulina 3 years
5 years
Agaricinese .
ssepiaria
Crepidotus sp. (?)
4 months
a few weeks
Marasmius oreades 6 weeks
3 months
peronatus
a few days
1 month
Collybia dryophila 1 week
1 month
cases the xerophytism of a fungus is only partial, so that desicca-
tion is fatal to the mycelium but harmless to the fruit-bodies.
However, the rapidity with which fruit-bodies, on the advent of
rain, develop upon sticks which have been dried up for weeks in
summer, points to the conclusion that the mycelium in the wood
must very frequently retain its vitality in a state of desiccation.
A somewhat striking laboratory experiment with Polystictus versi-
ii2 RESEARCHES ON FUNGI
color lends considerable support to these general field observations.
A stick, about 4 cm. thick and 30 cm. long, bearing a number of
fruit-bodies of the fungus in question, was gathered by myself and
kept in a dry state as a museum specimen. After an interval of
four years it was found that the fruit-bodies, on being moistened
in the usual manner, did not shed any spores, but appeared to be
discoloured and to have lost their vitality. The stick was then
given to Miss J. S. Bayliss for certain investigations which she
was then carrying on. It was set in a damp-chamber with one end
in water. Four weeks later Miss Bayliss observed that a number of
new fruit-bodies of Polystictus versicolor had begun to develop
upon it. In the course of a few weeks some of them attained
considerable size. 1 This observation seems to me to prove con-
clusively that the mycelium in the wood must have retained its
vitality for four years in the desiccated condition.
It is well known that the mycelium of Psalliota campestris,
when kept dry as "spawn" in compressed horse-dung bricks, re-
tains its vitality for years. According to Falck, 2 the mycelium of
Coprinus sterquilinus is still able to continue its development after
the horse-dung balls, in which it has existed, have been kept dry
for a year. In both these instances the vegetative part of the
fungus is resistant to desiccation, whereas the reproductive part
is not.
The xerophytic, hymenomycetous fruit-bodies growing on logs,
such as those named in the Table, have several features in
common. This is only what might be expected when it is
remembered that they are all adapted to the same external
conditions, i.e. to develop on a wooden substratum chiefly in
the cool and late autumn months. The points of agreement are
as follows :
1. They retain their vitality for months or years after desiccation.
2. They are all firmly built and resemble in consistency leather,
cork, or wood. Their toughness renders them inedible to slugs
and favours their persistence through periods of drought and frost.
1 Miss J. S. Bayliss, "The Biology of Polystictus versicolor (Fries.)," Journ. of
Economic Biology, vol. iii., 1908, p. 20.
2 R. Falck, Beitrage zur Biologie der Pflanzen, Bd. VIII., 1902, p. 317.
SCHIZOPHYLLUM COMMUNE 113
3. The upper surface of the pileus is usually hairy or woolly.
A means is thus provided for the rapid absorption of water on
the advent of rain. Free water placed at one edge of the pileus
quickly passes by capillarity over the entire upper surface. Since
in many species the fruit-bodies more or less overlap one another,
this arrangement may be of advantage in hastening recovery after
desiccation. The hairs, like those on the leaves of certain xero-
phytic Phanerogams, are doubtless of some service in diminishing
the rate of transpiration in dry weather. Direct evidence of this
is afforded by an experiment made by Miss J. S. Bayliss, 1 who
found that the removal of the hairs from the upper surface of a
pileus of Polystictus versicolor increased the rate at which the
process of drying took place.
4. They are able to withstand prolonged and severe frost (such
as occurs at Winnipeg).
5. They shed their spores at low temperatures. A number of
them can perform this function even at C. 2
6. Their attachment is unilateral. This is connected with the
fact that they grow on stumps, sticks, and fallen logs. The
dimidiate form of the fruit-bodies is as well adapted to the posi-
tion of the woody substratum as the radial form is to the position
of the earth in the Mushroom and Boleti, &c.
The Genus Schizophyllum. The genus Schizophyllum is unique
among the Agaricineae in that it is characterised by possessing
gills which are either partially or completely divided down their
median planes into two parts. We shall now proceed to interpret
this remarkable morphological fact in the light of observations made
upon Schizophyllum commune.
Schizophyllum commune is a species comparatively rare in
England but extremely common in Manitoba, where it is found
on sticks, logs, and stumps. The fruit-bodies, which are usually
attached laterally, attain a width of about 3 cm. They occur
singly or, more frequently, in imbricated groups. Their general
appearance is shown in Fig. 41, A and B, and Fig. 42. The gills
are in distinct fasciculi, each pair of deeper and longer ones being
1 Miss J. S. Bayliss, loc. ., p. 17.
Vide infra, Chap. X.
ii4 RESEARCHES ON FUNGI
separated by from three to five others which are shallower and
shorter (Fig. 41, E). The upper layer of the pileus presents a
FlG. 41. Schizophyllum commune a specialised xerophyte. A and B, fruit-bodies
seen from above growing on wood. Natural size. C and D, two fruit-bodies
seen from below and in section respectively. About twice natural size. B,
section through a pileus during wet weather showing the gills, which are split
down their median planes. F, section through a pileus after desiccation. E
and F about 12 times the natural size.
woolly appearance and is made up of tangled hyphse which extend
downwards towards the median planes of all the deeper gills.
SCHIZOPHYLLUM COMMUNE 115
The under layer of the pileus, the firm flesh which is produced
FlG. 42.Schizophyllui commune. The lower photograph shows a group
of fruit-bodies in the desiccated condition. The gill-fasciculi are
closed up. Natural size. The upper photograph shows the same
group of fruit-bodies after being revived. The gill-fasciculi are now
open. About $ natural size.
downwards to form the gills, thus becomes divided into radiating
portions (Fig. 41, E).
RESEARCHES ON FUNGI
The area of a fruit-body is increased by marginal growth.
The peripheral walls of the interlamellar spaces protrude outwards
as crenatures, and more or less resemble the heels of slippers
placed side by side in a row (Fig. 43). These crenated walls
constitute growing regions by means of which the older gills are
lengthened and new
ones added. Whilst a
pileus is extending by
marginal growth, the
interlamellar spaces
gradually widen.
When a space has at-
tained a certain width,
it becomes divided into
two down the middle,
owing to the formation
within it of a new gill
which arises as a short
median downgrowth
from the pileus flesh
(Fig. 43, a). The upper
half of every new gill
is undivided, but the
lower half is made up
of two plates, the inner
surfaces of which are
in contact and clothed
with loose hyphse (cf.
FIG. 43. Schizophyllum commune. Piece of a pileus seen
from below showing the arrangement of the gills.
a-<7, stages in gill development; h. part of the
woolly layer covering the top of the pileus and here
extended over the pileus margin ; i, interlamellar
space. Semidiagrammatic: the gills are represented
as cut through transversely so that the surfaces of
section lie in one plane. About 13 times the
natural size.
Fig.4LE). Agill,whilst
still very short, occu-
pies an isolated, sub-
terminal position within the interlamellar space in which it has been
formed. However, as growth proceeds, its distal end gradually
approaches the pileus margin and eventually joins with it
(Fig. 43, a-e). All gills at their first-formed, stipe ends are
shallow and only partially divided. However, at their peripheral
growing ends they gradually become deeper and more divided,
SCHIZOPHYLLUM COMMUNE
117
until at length they come to consist solely of two deep, apposed
plates. After a young gill has become connected with the
pileus margin, its two plates separate from one another slightly
at their peripheral ends. This separation of the gill plates, as
growth proceeds, becomes more and more marked, and at length
involves the pileus flesh. The peripheral end of every long and
deep gill thus comes to resemble in cross section the deepest
gills shown in Fig. 41, E. The whole gill system may be regarded
as being made up of branched fasciculi.
Schizopkyllum commune, as we have already seen, is a xero-
phyte. In moist weather the gills all look
vertically downwards, as in the Mushroom,
and spore-discharge takes place for days
from their hymenial surfaces (Fig. 41, E).
When dry weather comes, and the wooden
substratum gradually loses its water, de-
siccation of the fruit-body sets in. The
emission of spores soon ceases, and the
two halves of each gill begin to diverge
below (Fig. 44). As desiccation proceeds,
the gill plates become curled outwards
at their edges. When a fruit-body has
become quite dry, one finds that the
longest gills which have separated into
two halves to their bases, have covered in
the shorter ones. Each fasciculus of gills in cross section now
presents a very curious appearance (Fig. 41, F). It is evident
that the relative sizes and amounts of splitting of the different
gills are admirably adapted to facilitate the closing up of the
fasciculi. In a state of desiccation a fruit-body has its hymenium
completely hidden from external view, and the pileus is temporarily
provided below with a hairy covering.
Whilst in the dried condition a fruit-body can retain its
vitality for at least two years, and, with intermittent revivals,
for at least three years. When rain comes again, the woolly
upper surface of the pileus sucks water in by capillary attraction,
and the gill halves at once begin to unroll and reappose themselves
FIG. 44. Section through a
fasciculus of gills of Sckizo-
phyllum commune showing an
early stage in the divergence
of the gill plates. About
8 times the natural size.
n8
RESEARCHES ON FUNGI
in pairs. In the course of two or three hours the gills become
perfectly reconstructed, and they are then directed downwards
in the normal manner (Fig. 41, E, and Fig. 42). The hymenial
layer resumes its activity, and, after three or four hours of access
to moisture, the emission of spores is vigorously recommenced.
The mechanism involved in the closing and opening of a
pileus can be partially explained from anatomical considerations.
The main mass of each gili plate consists of downwardly running
FlQ. 45. Schizophyllum commune. Above, a transverse section
through a half-gill taken in a vertical direction ; below, another
transverse section taken in a horizontal direction, h, the hy-
menium ; s, the subhymenium ; t, the trama ; i, the inner free
hairy surface of the half-gill which becomes exposed on desic-
cation of the fruit-body. Magnification, 688.
tramal hyphse, which have very thick walls and are strongly attached
together at intervals. On the other hand, the hymenium and
subhymenium are composed of elements with relatively very thin
walls (Figs. 45). When a fruit-body dries up, the cell-walls of the
hymenial and subhyrnenial layers contract much more strongly
in the vertical direction than those of the tramal layer. This
being so, the curling up of each gill plate, when water is lost
from it, is a mechanical necessity. When a gill reabsorbs moisture,
the walls of the hymenial and subhyinenial layers expand to a
greater extent than those of the trama. The tramal hyphse are
SCHIZOPHYLLUM COMMUNE 119
thus permitted to straighten themselves again. The straightening
out of the gill plates, however, is brought about by something
more than mere cell-wall imbibition and stretching. This is
proved by the fact that the dry gills of dead fruit-bodies are not
capable of becoming entirely uncurled. Partial recovery of the
gills was observed : (1) In fruit-bodies which had lost their vitality
when kept for sixteen years in the dried condition, and (2) in fresh
fruit-bodies which were dried and then caused to absorb a solution
of 1 per cent, corrosive sublimate through their upper surfaces.
The first and major part of the straightening out of the gills we
may regard as a mechanical process connected with the swelling
of cell-walls. On the other hand, the final apposition of the two
plates of each gill appears to be brought about by the resumption
of turgidity by the hymenial and subhymenial elements. The finer
part of the whole readjustment, according to this interpretation, is
traceable to the semipermeable properties of living protoplasm.
The division of the gills of Schizophyllum into two plates is
significant in that it permits of the hymenial surfaces being pro-
tected during periods of drought. The rapid curling up of the gill
plates on the advent of dry weather must serve to check the rate
of loss of water from the fruit-body by limiting the amount of
gill surface exposed to the outer air. This closing oft' of most of
the transpiring gills at the beginning of desiccation, finds its analogy
in the curling up of the leaves of many xerophytic Phanerogams
under similar atmospheric conditions. However, I am not inclined
to think that reduction in the rate of transpiration is the chief
advantage gained by the opening out of the gill plates. Periods of
drought are often very long, and when they occur it may be of
considerable advantage for a fruit-body to have its delicate hymenial
surfaces, covered as they are with millions of spores, made as inac-
cessible as possible to various small marauding animals. However,
the exact ecological significance of the opening out of the gill
plates would best be elucidated in the tropics, where the genus
Schizophyllum is richest in species.
CHAPTER X
EXTERNAL CONDITIONS AND SPORE-DISCHARGE THE EFFECTS
OF LIGHT, GRAVITY, HYGROSCOPIC CONDITION OF THE AIR,
HEAT, ALTERATION IN THE GASEOUS ENVIRONMENT, AND
OF ANAESTHETICS
LIKE all other active processes of living organisms, the discharge of
spores can only be carried on when external conditions are favour-
able. It is now necessary to consider these conditions in detail.
The Effect of Light. Whilst in some species, e.g. the Mush-
room, the fruit-bodies can undergo perfect development in total
darkness, in a number of others the pilei cannot be produced
without a morphogenic stimulus given by light. Among the latter
are Lentinus lepideus and Polyporus squamosus. When a fruit-
body of either of these species is grown entirely in the dark, it
develops into a horn-like process without the least trace of a pileus
or hymenium (Fig. 16, D, p. 48, and Fig. 20, p. 58). It was found for
Polyporus squamosus, however, that, when the development of the
pileus has once been initiated in response to the stimulus of light,
if the fruit-body is then placed in the dark, further development
continues in a normal manner : the usual hymenial tubes are
produced and the hymenium gives rise to ordinary basidia which
liberate spores in continuous clouds. The production of spores in
clouds in the dark, which in one instance lasted for eleven days,
proves conclusively that, for Polyporus squamosus at least, the
liberation of spores is quite independent of light conditions. For
species of Polystictus, Lenzites, Schizophyllum, &c., spore-discharge
was found to be quite continuous. The alternation of night and
day appeared, as judged by the beam-of-light method, to make no
difference whatever to the rate at which spores left the fruit-bodies.
It is probably correct to state quite generally for the Hymeno-
mycetes that, whilst the morphogenic stimulus of light may or may
EXTERNAL CONDITIONS AND SPORE-DISCHARGE 121
not be necessary for the production of the hymeniurn, when once
the hymenium has begun its development, the basidia discharge
their spores quite independently of light conditions.
In the case of certain Ascomycetes, e.g. Ascobolus, it has
long been observed that spore-discharge is periodic, a certain
number of asci ejecting their spores each day. This phenomenon
has come more particularly under my notice in the case of
Ascobolus immersus growing on horse dung. The periodicity
depends on the alternation of day and night, and can be given
an easy ecological explanation. It is important for the purpose
of distribution that the ejected spores should be thrown clear of
obstacles, e.g. dung balls, &c. The asci are positively heliotropic,
and during the day always turn themselves in response to the
stimulus of light, so that they point toward open spaces. Such
an adjustment would be impossible at night. The periodic
discharge of asci each day is therefore of advantage in that it
ensures that these structures shall burst only after the light has
caused them to take up the most favourable positions for spore-
dissemination. On the other hand, as my observations have made
clear, spore-discharge in the Hymenomycetes is continuous and
does not take place at intermittent periods. The general arrange-
ment of a Mushroom or Polyporus is such that, under normal
conditions, the basidia never face obstacles. All that is required
for the successful liberation of the spores is that the basidia shall
shoot them straight outwards from the hymenium for a minute
distance. After being violently expelled from their sterigmata,
the spores drop into the spaces between the gills, in the hymenial
tubes, &c., and thus fall from the fruit-body and are carried off*
by air-currents without coming into contact with any impediment. 1
Almost without exception in the Hymenomycetes, the orientation
of the hymenium, and with it the direction of spore-discharge,
is finally determined by the stimulus of gravity, and is of such
a nature as to ensure that the spores shall fall out of the fruit-
body. The perfect indifference to light as regards spore-discharge
by the fruit-bodies of Hymenomycetes in comparison with certain
Ascomycetes is thus elucidated.
1 Vide infra, Chap. XVII.
122 RESEARCHES ON FUNGI
The Effect of Gravity. Gravity is the chief orienting stimulus
acting on the fruit - bodies of Hymenoruycetes. In Polyporus
squamosus, for instance, as we have already seen from the dis-
cussion in Chapter IV., it causes : (1) The stipe to turn the
rudimentary and terminal pileus into a horizontal position, (2) the
pileus to grow with a symmetry suited to the position of the
stipe, (3) the pileus flesh to grow parallel to the earth's surface,
and (4) the hymenial tubes to grow towards the earth's centre.
The stiped Agaricinese usually have stipes which are negatively
geotropic and gills which are positively geotropic.
Although the stimulus of gravity is of the greatest importance
in orienting the hymenium and the basidia which it contains,
it appears to have no direct effect on the process of spore-dis-
charge. When a hymenium has once started its development,
ripe spores continue to be developed and separated from the
basidia, independently of the direction of gravitational attraction.
Thus, if a gill be placed so that the basidia on one side look
upward or downwards or at any angle with the vertical what-
soever, spore - discharge takes place equally well in all cases.
Evidence of this was obtained by watching spores leave their
sterigmata with the microscope, and will be given in the next
chapter, which deals with the violent projection of spores from
the hymenium.
The Effect of the Hygroscopic Condition of the Air. It has
been mentioned already * that for Polyporus squamosus, so far as
it was possible to judge from the spore-clouds seen by daylight,
the liberation of spores takes place equally well both in a dry
and in a saturated atmosphere. For this species, therefore,
ordinary variations in the hygroscopic state of the atmosphere
do not appear to appreciably affect the rate of discharge of the
spores.
When a small portion of a pileus of Polyporus squamosus,
PsaUiota campestris, or Amanitopsis vaginata, &c., was placed in
a vertically disposed compressor cell (cf. Fig. 58, p. 167, and Plate IV.,
Fig. 29), so that the fall of spores could be watched with a hori-
zontal microscope, it was found that spores fell continuously when
1 Chap. VI.
EXTERNAL CONDITIONS AND SPORE-DISCHARGE 123
the chamber was saturated with moisture. When crystals of
calcium chloride were placed in the cell, the spores continued
to fall for some time, until the piece of pileus had shrunk
appreciably and was evidently drying up.
It can easily be observed with the beam-of-light method that,
if a fruit -body of Polystictus versicolor, Lenzites betulina, &c.,
is allowed to dry up slowly, when a certain amount of water has
been lost, the rate of spore-discharge becomes slower and slower.
As desiccation proceeds spore-fall ceases altogether. Insufficient
access to water must often, in nature as in the laboratory,
especially in the case of the xerophytic fruit-bodies growing on
logs ,and sticks, lessen the rate of spore-discharge and lead to a
corresponding increase in 'the length of the spore-fall period.
The general conclusion, to which numerous observations of
the kind just described have led me, is that, so long as a fruit-
body has sufficient moisture in itself, the dryness or dampness
of the atmosphere without makes no appreciable difference to
the rate of spore-discharge.
The Effect of Heat. The liberation of spores, like all other
vital processes, can only be carried on within certain limits of
temperature. Doubtless each species has its own particular
minimum, optimum, and maximum for this function.
In all the species so far investigated, the discharge of spores
takes place rapidly at ordinary room temperatures. It slackens,
however, when the temperature is sufficiently lowered ; but in
several instances it was found to continue even at the freezing
point of water, although with much diminished vigour. A slowing
down of the rate of spore-discharge also occurs when the tem-
perature is gradually raised above the normal; and when a
certain temperature has been reached, the hymenium becomes
altogether inactive. The maximum temperature for the discharge
of spores, however, is appreciably lower than the maximum for
vitality.
For the purpose of determining whether spore-fall still continues
at freezing point, a cold- room was made use of. The room had
two doors, one opening out-of-doors and the other into a passage
within the University building. The temperature of the room
124
RESEARCHES ON FUNGI
remained for hours, and sometimes for days, between and 3 C.
By opening the outer door for a few minutes the air of the room
could easily be reduced to C., and this temperature was often
maintained for several hours.
So far experiments have been limited to species which grow
upon wood and have proved capable of withstanding uninjured
the prolonged and severe frost of the Manitoban winter. Dried
fruit- bodies of Lenzites betulina, Polystictus versicolor, P. hirsutus,
Diedalea unicolor, and Schizophyllum commune were placed in
a damp-chamber with wet cotton-wool upon the upper surfaces
of their pilei.
They soon re-
vived, and at the
end of six hours,
upon being ex-
amined with a
beam of light,
they were found
to be vigorously
shedding spores.
A fruit-body, to
FlG. 46. Apparatus for demonstrating the fall of spores from u~ f^ci-prl wa<s
fruit-bodies at C. A glass dish u is placed on a wooden D eU> 1
shelf w in the cold-room. An inverted glass dish i is packed taken to the
round with snow s so as to leave the space within it unfilled. .
To the cork c is attached the fruit-body/, below which is COld-room and
placed a glass slide g for the purpose of catching the falling T . i
spores. About J actual size. pinned to a Cork
attached by
means of sealing-wax to the bottom of a small crystallising dish. This
was then inverted and packed round with melting snow contained
in another and much larger crystallising dish, as shown in Fig. 46.
After two hours, when the fruit-body had become cooled to freezing
point, the cold-room air was reduced to C. by opening the outer
door for a few minutes. The inverted crystallising dish, to which
the fruit-body was attached, was then lifted out of the snow, so
that fresh spore-free air at C. entered it. A glass slide (Fig. 46, g)
was then placed so that when the crystallising dish was replaced
in position, the fruit-body had its natural orientation, its under,
spore-producing surface looking directly down on the glass slide.
EXTERNAL CONDITIONS AND SPORE-DISCHARGE 125
After two hours the slide was removed and examined under the
microscope. Any spores which had fallen upon it could be detected
with ease.
The results, obtained from a number of experiments of the
kind just described, have served to convince me that Dssdalea
unicolor, Lenzites betulina, Poly st ictus versicolor, and P. hirsutus
continue to shed their spores at the freezing point of water.
However, the comparatively small number of spores which settled
upon the glass slides each hour showed that spore-discharge is
not nearly so active at C. as at higher temperatures. From a
succession of tests it was found that Lenzites betulina continued
to shed its spores at C. for at least three days. A fruit-body
of this species, whilst enclosed in the snow-chamber, set free
sufficient spores in a few hours to make a distinct, although faint,
macroscopic pattern of the gills upon a glass slide. Probably,
in all species which shed spores at C., the discharge of spores
continues for an indefinite period of time until the fruit-bodies
become exhausted. No spore-deposit was detected as being pro-
duced by Schizophyllum commune at C., although spores were
vigorously shed by this species at 5 C.
Ontogenetic study shows that the basidia of a hymenium come
to maturity successively, and part with their spores as soon as
these are ripe. The shedding of spores by Lenzites betulina,
Dasdalea unicolor, &c., in a snow-chamber indicates that in these
fungi the development of the hymenium can still continue at
the freezing point of water. At first, the fact that growth is
still possible in a hymenomycetous fruit-body at C., may seem
surprising, but parallel instances of growth at this and even lower
temperatures in other plants are by no means unknown. Thus
in Pfeffer's 1 list of cardinal points for growth, the minima for
Sinapis alba (Kirchner and de Vries), Ulothrix zonata (Klebs),
and Bacillus cyano-fuscus (Beyerinck) are given as C., and on
Arctic coasts, according to Kjellman, 2 algse flourish in sea-water
whose temperature falls to 1-8 and perhaps never exceeds C.
The fruit-bodies of species of Stereum, Corticium, &c., often appear
1 Pfeffer, Physiology of Plants, translated by A. J. Ewart, vol. ii., 1903, p. 77.
2 Kjellman, Bot. ZeiL, 1875, p. 171.
126 RESEARCHES ON FUNGI
to be at their best in the middle of an English winter, from
which fact it seems justifiable to conclude that cold weather is
favourable to their development.
The effect of high temperatures upon spore-discharge has been
investigated only in the case of Lenzites betulina. The fruit-body
to be tested was first determined to be freely shedding spores by the
beam-of-light method. It was then pinned to a cork fixed to a glass
plate, after which the plate was placed over a beaker, so that the
fruit-body assumed its normal orientation (cf. Fig. 37, p. 97). This
beaker with its cover, and another similar but uncovered beaker, were
then placed in the incubator, the air of which had been raised to the
desired temperature. After from thirty minutes to two hours, when
doubtless the fruit-body had assumed the temperature of the incu-
bator, the plate was quickly taken from the first beaker and set upon
the second. The air within the second beaker before this operation
was, of course, free from spores, whereas that of the first might still
have contained spores which had been liberated by the fruit-body
before this had become heated. After another fifteen or thirty
minutes, the second beaker was removed from the incubator and
immediately examined by the beam-of-light method. If spores had
been liberated into it, they could easily be seen floating in the air.
As a result of experiments of the kind just described, it was
found that the discharge of spores took place slowly at 29 C., but
not at 33, 43, or 46. The fruit-bodies, however, were not killed by
exposure for forty-five minutes to these high temperatures, for when
they were afterwards placed in a moderately heated room, in the
course of several hours they recovered and shed spores again in
abundance.
The modes of action of extreme cold and of extreme heat are
doubtless different. Extreme cold must slow down the metabolism
and hence prevent spore development. No injury in the case of
Lenzites, Dsedalea, and other similar fruit-bodies growing on logs,
results from a long exposure to very low temperature, e.g. from 15
to 40 C., such as occur often for weeks together in the course of
winter at Winnipeg. As soon as a fruit-body is warmed sufficiently,
spore-fall begins anew. Fruit-bodies of Lenzites betulina, Stereumpur-
pureum, and Schizophyllum commune were gathered from a wood-
EXTERNAL CONDITIONS AND SPORE-DISCHARGE 127
pile in March at about 17 C. after being exposed for several months
to severe frost. When brought into the laboratory they soon began
to shed their spores, and within a few hours produced well-marked
spore-deposits. 1 On the other hand, extreme heat probably causes
a heat rigor, for when some fruit-bodies of Lenzites betulina were
exposed to a temperature of 39 C. for half-an-hour and then cooled
to an ordinary room temperature, two hours passed by before the
fall of spores was resumed.
The range of temperature which permits of spore-discharge for
Lenzites betulina about to 30 C. probably coincides with the
range of temperature permitting the growth and development of the
spores. As soon as the spores are ripe they are probably shot off.
If one watches the discharge of spores from the basidia with the
microscope, one finds that spores which look ripe, i.e. which have
attained their full size and proper colour, do not long remain on
their sterigmata. The rate of spore-discharge seems, therefore, to be
an indication of the rate of spore development.
So far, opportunity has not been found for determining the range
of temperature within the limits of which the liberation of spores is
possible for succulent, non-xerophytic, ground Agarics which flourish
during summer. It seems to me probable, however, that for many
species, e.g. the Mushroom, the minimum temperature for shedding
spores is several degrees above the freezing point of water. To what
extent frost is fatal to the reproductive organs of Hymenomycetes
still requires investigation.
The Effect of Alteration in the Gaseous Environment. The
pileus of a small fruit-body of Marasmius oreades, about 1 inch in
diameter, was divided into three portions. One of them was placed
in a suitable glass vessel of about O75 litres capacity, through
which a strong stream of hydrogen was made to flow for ten minutes.
The stop-cocks were then closed. By similar means the second
portion of the pileus was surrounded by an atmosphere of carbon
1 Possibly the fruit-bodies began to shed their spores immediately they had
been unthawed and raised to the temperature of the laboratory. Unfortunately,
when these experiments were made, I had not developed the beam-of-light
method, and the formation of a macroscopic spore-deposit was relied upon as a
test for the liberation of spores.
128 RESEARCHES ON FUNGI
dioxide, whilst the third was set in a chamber containing ordi-
nary air. Glass slides were employed to catch any spores which
might fall.
The piece of pileus in air shed abundance of spores, a good deposit
outlining the gills being collected in the short space of ten minutes.
A thick deposit had formed in an hour, and in the course of twenty
hours tens of thousands of spores had collected. The piece of pileus
placed in hydrogen shed a few spores during the first hour. At the
end of this time it was removed to a new position on the glass slide.
During the subsequent nineteen hours scarcely a spore fell. The
few spores found on the slide with the microscope certainly did not
make up one five-hundredth part of the number which fell from the
piece of pileus placed in air. A similar result was obtained with
the piece of pileus placed in carbon dioxide. During the first
hour in that gas a few spores were liberated. The piece of pileus
was then pushed to a new position on the glass slide. During
the subsequent nineteen hours practically no further spores became
The conclusion to which the experiments just described appear
to point is that, in the absence of oxygen, spore-discharge soon
ceases. Doubtless for some time after a piece of pileus has been
placed in hydrogen or carbon dioxide, the basidia have access to
a certain amount of oxygen diffusing outwards from the pileus
through the hymenium. Possibly it is on this account that a few
spores still continue to be liberated for a short time after the
oxygen has been removed from the surrounding atmosphere. We
may conclude by analogy that the direct action of hydrogen on the
pileus is harmless, but that that of carbon dioxide may possibly be
poisonous.
Removal of oxygen from the atmosphere probably causes cessa-
tion of growth of the basidia. With this cessation of growth
the fall of spores must cease, for the continuous raining down
of spores from the gills depends on the successive development of
the basidia.
Two small pilei, one of Marasmius oreades and the other of
Psilocybe fcenisecii, were halved. One piece of each was covered by
a glass vessel containing air, and the other pieces were placed in a
EXTERNAL CONDITIONS AND SPORE-DISCHARGE 129
chamber of 0*75 litres capacity, through which a strong stream of
oxygen was made to flow for some minutes. The stop-cocks were
then closed. The pieces of pileus were set on glass slides so that any
falling spores might be caught.
After an hour, apparently equally thick deposits of spores had
been shed both in air and in the pure oxygen. The half-pilei were
then placed in new positions on the glass slides. During this opera-
tion air was kept out of the oxygen chamber by means of a strong
stream of oxygen passed through it. Five hours subsequently the
new spore-deposits were examined. They appeared to be equally
thick in both air and pure oxygen. The half-pilei were again
placed in new positions on the glass slides. These were once more
examined after an interval of eighteen hours. Heavy spore-deposits
resembling each other had again formed both in the air and in the
oxygen.
This experiment seems to prove that, in an atmosphere of pure
oxygen, the fruit-bodies of the two species examined continue to
develop their basidia and to shed their spores in the usual manner.
This need not occasion surprise, for many even of the higher plants
develop normally in pure oxygen or under a pressure of five
atmospheres of air. 1
The Effect of Anaesthetics. An observation with an anaesthetic
has already been made by Falck. He found that a fruit-body of
Agaricus nebularis, on being subjected to chloroform vapour,
ceased to shed spores, and he drew the conclusion from this fact
that spore-liberation is an active process. 2 Experiments with
anaesthetics, however, do not decide whether the spores are set
free by a process of growth and thus simply fall when ripe like
apples, or whether, on the contrary, they are shot outwards from
their sterigmata with force. In the next chapter this matter will
be dealt with in detail.
In order to test the effect of ether vapour upon the liberation
of spores, the following method was resorted to. A piece of cork
was fixed by means of sealing-wax to the middle of a circular
1 Pfeffer, Physiology of Plants, vol. i. p. 540.
2 R. Falck, "Die Sporenverbreitung bei den Basidiomyceten/' Beitrage zur
Biologic der Pflanzen, Bd. IX., 1904, p. 27, footnote.
I
130 RESEARCHES ON FUNGI
plate of glass, and to it a fruit-body to be tested was pinned.
The glass plate was then placed on the ground top of a cylindrical
glass jar of 1-25 litres capacity, so that the fruit-body had its
natural orientation (cf. Fig. 37, p. 97). A piece of blotting-paper
was attached with sealing-wax to the bottom of the jar.
The fruit-body was first tested in the usual way with a beam
of light to find out whether spore-discharge was taking place.
In all cases a cloud of spores could easily be seen coming from
the lower surface. When it had thus been determined that
spores were being freely liberated, the glass cover, with the fruit-
body attached, was removed, inverted, and placed on a table.
Fresh spore-free air was caused to enter the now open jar. By
means of a pipette O5 cc. of Squibb's ether was then quickly
dropped on to the blotting-paper in the jar and the latter
immediately inverted over the glass cover, to which it became
closely attached by means of vaseline. When a fruit-body is
upside down it is unable to liberate any of its spores into the
air in a glass chamber. So long, therefore, as the fruit-body
was kept inverted, the air in the jar above it remained spore-free.
When it was desired to find out whether spores could still be
liberated, the anaesthetised fruit-body was turned into the normal
position again by means of another inversion of the jar. The air
beneath the now downwardly-looking hymenium was then examined
for spore contents with a beam of light. It was found that, when
the jar was placed upright again two minutes after its first
inversion, no spores fell into the air within. The ether vapour,
therefore, caused cessation of spore-discharge in two minutes.
When the ether was added to an upright jar, and the cover,
bearing a normally oriented fruit-body, was placed on the top,
at first the spore clouds could easily be seen coming off from the
underside of the fruit-body with the beam of light ; but the
spore stream quickly diminished in density and its emission
ceased after about two minutes. The spores which had already
entered the jar then spread themselves evenly in the air which
it contained.
When the jar in the first described experiments was placed in
the upright position a few minutes after the ether had been
EXTERNAL CONDITIONS AND SPORE-DISCHARGE 131
added, the fruit-body was always found to have lost its power of
shedding spores. Not a single spore could be seen floating in the
beam of light, nor, so long as the fruit-body remained subjected
to the anaesthetic, were any spores liberated. When, however, the
fungus was removed from the glass jar and exposed to ordinary
air, it gradually recovered. It was found that, even after treat-
ment with ether vapour for a week, recovery could still take place
and active spore-discharge be resumed. The length of time during
which fruit-bodies were exposed to ether vapour, and the length of
time required for recovery of the spore-liberating function after
removal from the anaesthetic, are given in the following table:
Lenzites betulina.
0-5 cc. Squibb's ether in a 1'25 litre jar.
Time taken for Recovery of the Spore-
Length of Exposure to the liberatinsr Function after Removal
Ether Vapour. from Ether Vapour.
5 minutes .... Less than 30 minutes.
30 minutes .... More than 2 hours.
12 hours ..... About 3 hours.
, j More than 3 hours 45 minutes.
I Less than 4 hours 35 minutes.
7 days . . . . .6 hours 30 minutes.
It is clear that the longer the fruit-bodies were exposed to
the anaesthetic, the longer was the time required to recover from
the effects.
The chief result of these experiments is to show that spore-
discharge may be inhibited by ether without any apparent
permanent injury to the fruit-body. The shooting off of the
spores, and probably their development, ceases under the in-
fluence of ether just as does protoplasmic movement in the cells
of higher plants and the reactions to mechanical stimuli in the
leaves of Mimosa pudica, the stamens of Berber is, &c. As in
these cases, the active process is resumed again when normal
conditions are allowed to supervene.
Chloroform has a similar effect to ether. 0*5 cc. of chloroform
was introduced into the 1-25 litre jar in the manner already
described. Under these conditions the liberation of spores ceased
in about one minute. The fruit- body was exposed to the chloro-
132 RESEARCHES ON FUNGI
form vapour for five minutes and then placed in ordinary air.
Recovery of the spore-liberating function took place after about
fifteen minutes. It might be expected from analogy that chloro-
form would prove more poisonous to the fruit-bodies than ether.
No attempt, however, has been made to obtain an experimental
basis for this assumption.
CHAPTER XI
THE VIOLENT PROJECTION OF SPORES FROM THE HYMENIUM
METHODS I., II., III., IV., AND V..
IN order to understand the arrangements for liberating the spores
from the fruit-bodies of Hymenomycetes, it is of great importancelto
bear in mind that the spores are very adhesive. After they have
settled on paper, glass, j a pileus, or stipe, the most violent shaking
will not separate them from the surface to which they have become
attached. They cling to each other with great tenacity, for from
spore-deposits one may scrape up spore ribbons several millimetres
long. If a ripe Mushroom or other fruit-body be turned upside
down so that the spores after leaving the sterigmata settle upon the
basidia and paraphyses of the hymenium, when the fruit-body is
again placed in the natural position not one of the fallen spores
succeeds in freeing itself. One can see with the microscope that the
spores remain fixed where they fell. When a fruit-body is inverted
for an hour, some millions of spores leave the sterigmata and settle
on the gills. If the spores were not adhesive, on replacing the fruit-
body in its natural position and observing with the beam-of-light
method, one should be able to see these millions of spores falling in
the form of a dense and very temporary cloud. No such cloud,
however, can be detected. These and other observations of various
kinds have convinced me that, if a spore after leaving its sterigmata
happens to touch the hymenium in its fall, even when it strikes it
very obliquely, it immediately gets stuck there, and never succeeds
in reaching the outer air.
In discussing the general structure of the fruit-bodies it was
pointed out that in many cases the hymenium is disposed for the
most part in almost vertical planes. In the Agaricinese it is situated
on the surfaces of very acutely wedge-shaped gills, and in the
Polyporese it lines the surfaces of very slightly conical tubes. In
134 RESEARCHES ON FUNGI
many fruit-bodies of Agaricinese the declination of the gill surfaces
from the vertical is only from one to three degrees.
Whilst reflecting on the adhesiveness of the spores and the ver-
tical position of the hymenial surfaces, I asked myself the question :
By what means are the spores enabled to fall from the basidia without
contact with one another, and in such a manner that they find their
way down hymenial tubes or between gills without becoming attached
to the sides ? Taking into consideration that the horizontal basidia
are crowded one above the other (cf. Fig. 56, p. 165, and Plate I.,
Fig. 3), it was argued that if the adhesive spores merely fell from
the sterigmata in a passive manner, they would very frequently fall
upon one another, and that of necessity they would fall rather
inwards toward the hymenial surface than outwards, owing to the
tendency they would have to swing beneath the sterigmata. On the
assumption of passive fall it seemed impossible to imagine how the
adhesive spores could be liberated. Before any observations were
made, therefore, it appeared to me highly probable that in some
manner the spores must be projected for a short distance straight out
from the hymenium in which they are produced. This deduction
has been verified in various ways. My observations seem to indicate
that violent spore-projection is of general occurrence throughout the
Hymenomycetes.
So far as I am aware, hitherto Brefeld alone has made observa-
tions on the separation of spores from the basidia. In the case of
Amanita muscaria 1 he simply says, " In diese [the spaces between
the gills] werden die Sporen durch schwache Ejaculation geworfen
und fallen dann zu Boden." In a footnote in his account of the
life-history of Coprinus stercorarius? he states that the spores are
shot outwards in consequence of the bursting of the sterigmata. He
believes himself to have seen small drops left on the sterigmata, and
also on the spores after spore-discharge, and states that all four
spores are shot off from a basidium simultaneously. With regard to
violent spore-ejaculation being a fact, I am in entire agreement with
Brefeld, but am unable to confirm his description of the process in
detail. The spores, so far as my experience with several species of
1 Brefeld, Botanische Untersnchungen iiber Schimmelpilze, III. Heft, p. 132.
2 Brefeld, loc. cit., pp. 65, 66.
THE VIOLENT PROJECTION OF SPORES
135
Coprinus and of many other genera goes, are never shot off simul-
taneously. I have also not been able to obtain any evidence that
the spores are projected forwards owing to ejaculation of the contents
of the basidia. The mechanism of spore-discharge, however, will be
discussed more conveniently in the next chapter.
Several methods have been used to determine whether or not the
spores are shot off the sterigmata. The first one, which seemed for
some time to give convincing evidence of spore-projection, led to the
discovery of an unexpected optical illusion.
Method I. The first method employed for observing spore-fall
microscopically was that of placing hymenial surfaces in vertical
planes and observing them from
above with an ordinary upright
microscope.
Through the middle of some
of the hymenial tubes of a freshly
grown fruit- body of Polyporus
squamosus, a transverse section
1-2 mm. thick was made (Fig. 47).
This was then placed on a glass
slide, covered with a cover-glass,
and looked down upon from above
with the low power of the micro-
scope. Immediately the remark-
able fact was observed that the spores were apparently being shot
outwards from the hymenium towards the middle of the tubes.
Apparently one could see them taking part of their curved and out-
ward course through the air. They were also seen to settle below on
the glass slide on the average at a distance of 0'1-0*2 mm. (6-20
times their own length) from the hymenium. In this way the spores
collected in a zone about 0'5 mm. wide around the base of each tube.
In the course of a few minutes I watched the discharge of hundreds
of spores. Not only to myself, but to others, the apparent bombard-
ment of the spores into the lumina of the tubes seemed to afford
clear and convincing proof of the violent projection of the spores
from the basidia.
Similar observations to those just recorded were then made upon
FIG. 47. Diagram to show the shape of
a transverse section through the hy-
menial tubes of Polyporus squamosus.
About 6 times natural size.
136 RESEARCHES ON FUNGI
other species of Polyporus, and also upon species of Polystictus,
Dsedalea, and Boletus. The hymenial tubes of many members of the
Polyporeae are extremely narrow. Thus with the aid of the drawing
apparatus and a stage micrometer, it was found that the diameters
of the tubes at the mouths were on the average : for Polyporus
hirsutus, O'S-0'4 mm. ; for Fomes vegetus, G'15-0'2 mm. ; for
Fomes igniarius, O'lo mm. ; and for Polystictus versicolor, 0-2-
0'25 mm. In Polyporus hirsutus and Polystictus versicolor, for
which species alone fresh material was available, the spores seemed
to be bombarded from the hymenium just as in the case of Polyporus
squamosus. They appeared to be projected outwards from the
hymenium and were seen to descend near the centres of the tubes,
at the mouths of which they collected in heaps. Polyporus hirsutus
had tubes in the centre part of its fruit-body 2 cm. long. However,
by making transverse sections at different heights it was observed
that the spores were discharged throughout the whole length of a
tube. For Polystictu versicolor the tubes were often only - 2 mm.
wide. Yet even in these the spores seemed to be shot outwards
from the hymenium. They appeared to travel a distance of about
01 mm. toward the middle of the tubes before the horizontal velocity
had been reduced to zero.
The species of Boletus investigated and the diameters of their
pores, as given by Massee, 1 were as follows: Boletus chrysenteron,
1-1-5 mm.; B. felleus, up to 1 mm.; B.flavus, -1 mrn. ; B. subto-
mentosus, -1 mm. ; B. scaber, O'5-l mm. ; B. badius, O'5-l mm.
Here, again, sections 1-2 mm. high were taken transversely through
the hymenial tubes, and looked into from above with the low power
of the microscope. In each, again, the spores were apparently shot
off from the hymenium into the tubes. In the wider tubes the spores
were seen to collect at the mouths in a zone around the walls, and in
the narrower ones they gradually formed a central heap. The im-
pression gained was that the spores were projected horizontally on
the average O-2-O'l mm., or about the same distance as for Polyporus
squamosus. Dasdalea unicolor (a very common fungus at Winnipeg)
behaved like the Boleti.
In order to observe the fall of spores in members of the Agari-
1 G. Massee, British Fungus-Flora, 1892, vol. i.
THE VIOLENT PROJECTION OF SPORES 137
cineae, tangential sections about 1-2 mm. thick were made through
the pilei, so as to cut the gills transversely. The sections were then
placed on a microscope slide, by which means the hymenial surfaces
took up a vertical position (Fig. 48). Sometimes the sections were
placed in a glass cell closed with a cover-glass, but this precaution for
keeping off air-currents was usually found unnecessary in a quiet
room where the air was still. The spores appeared to be violently
projected from the hymeniurn into the spaces between the gills in all
the species which were examined. As in the case of Polyporus
squamosus, however, only part of the path of each spore could be
observed, owing to the fact that only one plane can be focussed at
one time by the. microscope. The discharge of the spores could
usually be detected almost immediately the section had been made,
and continued for some minutes
until loss of water from the gills
interfered with the process. In
small, closed glass chambers,
where loss of water vapour was
prevented, the discharge of
spores continued in some in-
stances for several hours. The
Spore zone of discharged Spores with gills. The hymenial surfaces are
c vertical. About 4 times natural size.
on the glass slide between two
gills and adjacent to the base of each was in most cases about
0*2 mm. wide. The impression was gained that the spores had been
projected about O'l mm. before the horizontal motion was destroyed.
The Agaricinea3 used as material for these observations consisted of
thirty-one species common in the Midlands of England, and included
in the following genera: Psalliota, Stropharia, Anellaria, Galera,
Amanitopsis, Amanita, Lactarius, Russula, Panreolus, Psilocybe,
Colly bi a, Cantharellus, Laccaria, Hygrophorus, Nolanea, Hypholoma,
Marasmius, Entoloma, Mycena, and Armillaria.
The first method of observing spore-fall with the microscope
in the Polyporeae and Agaricinese appeared to yield two facts in
favour of the supposition that the spores are violently discharged
from the sterigmata: (I) The spores could apparently be seen
travelling horizontally away from the basidia, and (2) the spores
138
RESEARCHES ON FUNGI
settled some distance from the vertically-placed hymenium. The
latter fact I regard as good evidence of spore-projection, but the
former, which for some time seemed to yield convincing proof of
the phenomenon, has been found by subsequent investigation to
be misleading and based upon a curious optical illusion. As a
result of further observations and calculations it can be shown
that the spores are really projected from the basidia with a high
velocity, but nevertheless it is most improbable that one should
observe directly the horizontal motion of a spore because it is
performed too rapidly.
The apparent travelling
outwards of a spore
from the vertically-
placed hymenium,
which one can observe
so easily in Agaricinese
and Polyporese, is really
no travelling outwards
at all. The spores, when
seen in motion, are in
reality falling vertically.
For some months this
illusion deceived me,
as, indeed, it had de-
M
N
^?
FlG. 49. Diagram of a tiny cylinder MN on
slide S, viewed from above in the direction
the
arrow O with the low power of the microscope.
ABCD is a section of the cylinder within the
range of focus. X and Y show the paths of two
spores falling vertically. To the right is shown
how the section and the paths of the spores appear
to the observer.
ceived others to whom
I had shown it. How-
ever, the possibility of the apparent fact of horizontal movement
of the spores being in some way deceptive, caused me, after a while,
to make a careful study of the appearance of vertical surfaces
under the microscope.
A tiny brass cylinder was constructed, placed upright on a glass
slide, and observed from above with the low power of the microscope.
It was found that, wherever placed in the field, any part of the
vertical surface observed appeared to slope at an angle from the
vertical. The result of the observations may best be made clear
by means of a diagram (Fig. 49). Let MN be the cylinder standing
vertically upright on the glass slide S, and let the arrow O indicate
THE VIOLENT PROJECTION OF SPORES
139
II
B
the direction in which the cylinder is viewed with the microscope.
Let A B C D be a section of the cylinder placed within the range
of focus. Then to the observer the section will have the appearance
of a truncated cone, abed. The truly vertical sides of the section
of the cylinder will appear inclined as shown in the figure. 1 Now
let the arrows X and Y indicate the
truly vertical paths of two spores falling
parallel to the sides AB and CD of the
cylinder. Then, when observed with the
microscope, the course of the spores will
appear to be as indicated by the arrows
x and y, i.e. the illusion will be created
that the spores are moving more or less
horizontally outwards from the cylinder.
The apparent bombardment of the
spores into the spaces between the gills,
which one sees on looking vertically
downwards upon a section like that in
Fig. 48, may now be explained. Let
A A in Fig. 50 represent a vertical section
taken transversely through three of the
gills, and let the arrows placed parallel
to, and at a little distance from, their
vertical sides, represent the true paths
of six spores falling vertically. Then, as
shown at BB, when the low power ob-
jective of the microscope is placed in the
position of the arrow O, one apparently
observes spores being shot outwards from
both sides of the gill immediately below,
and, when one observes in the direction
FIG. 50. Above at AA is shown
a transverse and vertical section
through three gills of a piece
of a pileus like that in Fig. 48.
When observed from above in
the directions of the arrows O,
P, and Q, the range of focus
is supposed to be between the
dotted lines. The four arrows
between the gill-sections indi-
cate the paths of four spores
falling parallel to and about one-
tenth of a millimetre from the
hymenial surfaces. Below at
BB is shown the apparent shape
of the parts of the gills in focus
and the apparent paths of the
spores. The latter, although
falling vertically, appear to be
shot outwards from the hy-
menial surfaces into the spaces
between the gills.
indicated by either of the arrows P or Q, one apparently sees the spores
being shot outwards from two gills into the interlamellar spaces.
1 The explanation of the phenomenon seems to be due to the fact that the
area of the objective is large compared with diameter of the cylinder, so that
different parts of the objective, as it were, can see different parts of the cylinder.
With the low power of the microscope one can see simultaneously both sides of
an ordinary glass slide placed vertically.
140 RESEARCHES ON FUNGI
It is now clear to me that the apparent shooting out of spores
from the vertically-placed hymenium in the many Agaricinese and
Polyporese observed by my first method is simply an illusion.
During the apparent bombardment of hundreds of spores into a
cross section of a tube of Polyporus squamosus, or into the spaces
between two gills in a Mushroom (which one sees in looking down
upon such sections as those represented in Figs. 47 and 48), one
does not really see a single spore performing any part of its
horizontal motion. The spores are falling vertically as soon as
ever perceived. By methods to be described in Chapter XVII. it
has been found that for Amanitopsis vaginata the total horizontal
distance to which the spores are projected, namely, about 0'2 mm.,
is accomplished in approximately only 4^ second, and that the
initial velocity with which each spore is shot forward is about
400 mm. per second. From a consideration of these remarkable
figures, and also the fact that the spores must be considerably
magnified in order to be seen at all, it seems to me very improbable
that the human eye, aided as it must be by the microscope, will
ever be able to detect the horizontal motion of a spore. Whether
or not it is possible to do so must be left to the experimental
psychologist. That the downward motion of a spore, which is
performed at a constant speed in response to gravity, should be
observed as described is easily understood, for it is performed
relatively much more slowly and for a much longer distance than
the horizontal motion. In the case of Amanitopsis vaginata the
terminal vertical velocity is only about 5 mm. per second. In
most other species, where the spores are smaller, the velocity is
usually only 1-2 mm. per second. 1 These theoretical considera-
tions, which it has been necessary to introduce in this place in
order to explain the results of observations Avith Method I., will
doubtless become clearer to the reader when the curious nature
of the "sporabola" has been discussed in a subsequent chapter.
Observations, with the special object of seeing the horizontal
flight of particular spores on leaving the sterigtnata, were made
with sections of Polyporus squamosus like that in Fig. 47 on several
occasions, but they gave only negative results. With a vertical
1 Vide infra, Chaps. XV. and XVI.
THE VIOLENT PROJECTION OF SPORES
141
microscope a ripe spore on its horizontal sterigma was carefully
watched until it Avas discharged. One mo-
ment it was in view : the next it had dis-
appeared, but in what direction could not
be detected. The eye had not been able to
follow the motion.
Method II. The second method em-
ployed to determine whether or not violent
spore-projection takes place was as follows:
A piece of a gill, 4-5 mm. high and 2-3
mm. broad, was cut from a ripe fruit-body
of Amanitopsis vaginata and placed in a
vertical, but inverted, position on a tiny
glass shelf in a vertically-disposed compressor
cell. A horizontal microscope, with a magni-
fication of about 25 diameters, was then
employed to observe the fall of spores from
the piece of the gill when seen end-wise (cf.
Plate IV., Fig. 29). The gill segment thus
came to be so placed that the sides bearing
the hymenium were inclined to the vertical,
as shown in Fig. 51. The hymenium, there-
fore, looked very slightly upwards. Usually
it was found convenient to concentrate the
attention on one side of the gill, and in all
cases, by tilting the compressor cell held in
a clamp, the side in question was made to
incline distinctly upwards at a slight angle
from the vertical. It was argued that, if the
adhesive spores only drop off the sterigmata
passively, they would never be seen in the
air, whereas, if indeed they are projected
violently outwards, although one might not
be able to see them in their horizontal flight,
yet one should often be able to see them falling vertically at a little
distance from the gill surface.
On actually making the observations, it was found that the
FlG. 51. Diagram show-
ing a piece of a gill
inverted and placed on
a tiny horizontal shelf,
AA, in a vertically-
disposed compressor cell.
The piece of gill is seen
edgewise with the hori-
zontal microscope. H is
the hymenium. S, S,
show the paths of the
spores when seen falling.
The spores first come into
view about one-tenth of a
millimetre from the hy-
menium. About 20 times
natural size.
1 42 RESEARCHES ON FUNGI
spores came suddenly into view at a distance of O1-O2 mm. from
the gills. As soon as seen, the spores were falling vertically at a
constant speed. 1 The diagram, Fig. 51, shows the courses of a few
spores as seen with the horizontal microscope. These observations
seem to me to afford conclusive proof of violent spore-projection.
They ma} 7 be repeated without difficulty. One may have to wait
a few seconds or minutes before a spore springs into view, but this
is merely a question of patience. The species used for these ob-
servations, in addition to Amanitopsis vaginata, were: Psalliota
campestris, Marasmius oreades, and Polypwus squamosus. For
the Polyporus a piece of the wall between two hymenial tubes
took the place of a piece of gill.
The horizontal distance from the hyinenium, at which a spore,
when first perceived, appeared to be, was compared with the dis-
tance between tiny irregularities on a silk thread of the Ramsden
eyepiece of the horizontal microscope. The latter distance was
then carefully measured with a standard micrometer scale. After
a number of observations had been made in each case, the con-
clusion was arrived at that the spores of Amanitopsis vaginata
are often shot to a horizontal distance of i mm., and that those
of the other three species are often shot T \j- mm. and sometimes
a little further.
Method III. The third method employed for demonstrating
the violent projection of spores from the sterigmata is perhaps
the most conclusive of all. It can be carried out most certainly
and easily with fruit-bodies of the Coprini. Coprinus plicatilis
was made chief use of in these experiments, but C. comatus
and C. micaceus gave similar results. One takes a gill that
is shedding spores and lays it flat in a closed compressor cell, and
observes it from above with the low power of an ordinary micro-
scope. Under these conditions the basidia are pointing upwards.
One can then very readily observe the disappearance of the spores
from the sterigmata near the " deliquescing " gill edge, for it is
here and here alone in the Coprini that active discharge of spores
takes place (Plate II., Fig. 12). If one focusses a plane at a little
1 The air in a compressor cell is practically quite still. The spores fall verti-
cally in it, and are not carried about by convection currents.
THE VIOLENT PROJECTION OF SPORES 143
distance above the plane of the hymenium, so that the basidia
are just out of view, one finds that spores spring into view and
immediately disappear again. This proves conclusively that the
spores have been projected violently upwards from the sterigmata.
The fine adjustment screw of the microscope was carefully cali-
brated by the glass plate method, and it was then found by measure-
ment with it that in the case of Coprinus plicatilis the spores
were projected upwards, so that they came into view in a plane
O08-O12 mm. above the plane of the spores on the sterigmata.
It has been found possible to observe the upward projection of
spores in the Mushroom, and also in a species of Psilocybe. In
these cases, however, observations can only be made with consider-
able difficulty. In the ,Coprini the spores in a zone parallel with,
and adjoining, the deliquescing gill edge are all being discharged
almost simultaneously (Plate II., Fig. 12). The gills of Coprini are
also very thin and allow ample light to pass through them. In
all other species of Agaricinese, however, the spores are discharged
irregularly over the whole surface of a gill and there is no special
region of activity. Adjacent basidia are in very various stages of
development. When one looks down on a piece of gill of one of
these fungi, one but rarely sees the spores disappear from a basidium.
This is due to the fact that the ripe basidia are relatively far apart.
The gills are also much thicker than in the Coprini and allow but
little light to pass through them.
The observations on the Mushroom were carried out in the
following manner. A fresh specimen was obtained from a field
and part of one of the pink gills placed flat in a closed compressor
cell. The latter was then placed on the stage of the microscope
and this tilted to an angle of about 45. The tilting ensured that
if a spore was shot off a sterigma in the field of view, it would
remain longer in view than it would if the microscope were vertical.
A plane situated a short distance above the hymenium was focussed
so that one could not see any of the basidia distinctly. After
several hours of watching, on three separate occasions a spore was
clearly seen to come into view in the plane above the hymenium
and to travel a little way across the field of view before disappearing.
The only explanation of these observations seems to be that the
i 4 4 RESEARCHES ON FUNGI
spores had been shot off the sterigmata just as in the Coprini. A
species of Psilocybe yielded a similar result.
Method IV. A piece of a gill of a Mushroom was placed flat
in a closed compressor cell and observed from above with an
ordinary vertical microscope. An endeavour was made to see the
spores leave the sterigmata of individual basidia. It was argued
that, if the spores merely fall passively from the sterigmata, after
liberation they ought to lie below their respective sterigmata,
whereas, if they are discharged violently, they should often take
up other positions.
Apparently ripe basidia were focussed and watched. After some
D _
jj w tx s?
FIG. 52. The successive and violent discharge of the four spores from the
basidium of Psalliota campestris. Part of a gill was laid flat in a compressor
cell. The basidium looked upwards and was observed from above. X the
basidium, with its four ripe spores. The appearance of the basidium imme-
diately after the discharge of spores 1, 2, 3, and 4 is shown at A, B, C, and
D respectively.
hours had been spent at this task, a basidium was seen to discharge
all its spores. Sketches were made after the discharge of each
spore and are reproduced in Fig. 52. When one watches the dis-
charge of a spore, all that one can see is that the spore suddenly
disappears from its sterigma and immediately appears again in a
new position on the hymeniurn. In Fig. 52, X shows the appear-
ance of the four spores on the basidium before discharge, and
A, B, C, and D illustrate what was seen immediately after the
discharge of spores Nos. 1, 2, 3, and 4 respectively. It is clear
that the spore No. 2 (B) must have jumped over No. 4 to get
into the position it came to occupy after discharge. Similarly,
No. 4 (D) must have jumped over No. 3. A study of this case
THE VIOLENT PROJECTION OF SPORES 145
and many others, where only the last spore or the remaining two
or three spores were observed to be discharged, has convinced me
that the spores when liberated must be shot upwards for a little
distance before falling on to the hymenium. Doubtless the spores
were shot not quite vertically upwards, but nearly so. Hence the
various positions of the spores after settling.
In the Coprini, it is exceedingly easy to observe the discharge of
spores from the basidia near the edge of a " deliquescing " gill. As
before, it is necessary to place the gill or piece thereof flat in a closed
compressor cell to prevent too rapid loss of water and consequent
collapse of the basidia. With the low power of the microscope one
can then observe large numbers of basidia actively shedding their
scores (Plate II., Fig. 12). The phenomenon has quite a fascination
of its own. The spores, after disappearing from the sterigmata, very
frequently immediately reappear on the hymenium at some distance
from the basidia on which they have been developed. There is
no essential difference between the Mushroom and the Coprini in
regard to what one sees by using Method IV. Fig. 52 might
equally well apply to the basidium of a Coprinus comatus or
C. plicatilis.
One fact which is yielded by the above observations, and has an
important bearing in explaining the mechanism of spore-discharge,
is that the four spores of a basidium are not shot off their sterigmata
simultaneously but successively. The succession of discharges in
the particular instance shown in Fig. 52 occupied twenty minutes.
There was an interval of a few minutes after each one before the
next took place. It is quite certain that usually the four spores of
a basidium are not discharged together. When one looks at the
hymenium of a Mushroom gill in face view, it is easy to observe that
many of the ripe basidia have only one, two, or three spores left upon
them. In many instances the successive discharge of two or three of
the spores was actually watched. In Coprinus comatus one can
make similar observations with great ease. I have watched hundreds
of basidia discharge their spores in this species, yet never once have
I seen all four spores of a basidium discharged together. Here, as in
the Mushroom, the four spores of a basidium disappear from their
sterigmata one by one, in the course of one or a few minutes.
K
146
RESEARCHES ON FUNGI
I
The same results were obtained with Coprinus pUcatiUa and
C. micaceus. In the already-mentioned footnote to Brefeld's
description of C. stercorarius, it is stated that the spores are all
discharged simultaneously. Although I have not had an oppor-
tunity of examining this species, I think it highly probable that it
discharges its spores in the same manner as other Coprini, and that
Brefeld's statement will not be corroborated by further observation.
Whilst using Method I. it was often easy to observe single ripe
basidia and to watch the disappearance of some of the spores. Thus,
in the case of Poly-
porus squamosus, in
one instance three
spores left a basi-
diuin at intervals of
twenty seconds,
whilst the fourth
remained on its
sterigma for some
minutes afterwards
and was not seen to
disappear. In an-
other instance two
of the four spores
left a basidium with-
in a few seconds of
one another. A large
number of observa-
FIG. 53. Diagram showing the appearance of part of the
hymenium at the base of a section of a hymenial tube
of Polyporus squamosus (cf. Fig. 47. p. 135). The arrow
indicates the direction of observation. A basidium
bearing four ripe spores and the top of the glass slide
were included in the range of focus. The figure shows
the position of one of the spores on the glass slide
after being discharged to six times its own length from
the basidium.
tions, obtained by using Methods I. and IV., have convinced me that
in very many species the spores are discharged from a ripe basidium,
not simultaneously, but successively one after the other. It seems
to me highly probable that this is a general rule throughout the
Hymenomycetes.
Method V. A transverse section through the hymenial tubes of
Polyporus squamosus (Fig. 47) was made and placed on a glass slide
in the same manner as was done for Method I. The basidia thus
came to occupy their normal horizontal positions. The discharge of
spores was watched with the ordinary vertical microscope. I con-
THE VIOLENT PROJECTION OF SPORES 147
centrated my attention upon a ripe basidium which projected
horizontally from the hymenium in one of the tubes at a very short
distance above the glass slide (Fig. 53). So near was the basidium
to the slide that I was able to have both spores and glass surface
within the range of focus at the same time. After I had watched for
a long time, one of the spores suddenly left the basidium and became
deposited on the glass slide some six times its length from the
basidium. It had therefore been shot along just above the glass
surface for a distance of 6 x 13 /^ or 0*078 mm. The observation just
recorded, although the only one of its kind that I have been able to
make, seems to give another convincing proof of the fact of violent
spore-projection. The actual movement of the spore from the
basidium to its place of rest on the glass slide was not seen, although
I was watching with concentrated attention for the express purpose
of observing it. However, certain mathematical considerations soon
to be treated of, indicate that it is highly improbable, if not im-
possible, that one should perceive the horizontal motion, however
carefully one might make one's observations.
CHAPTER XII
THE MECHANISM OF SPORE-DISCHARGE
IN the last chapter it was shown that the spores of Hymenomycetes
are discharged frorn the sterigmata in a violent manner. The
mechanism by which this process is brought about will now be
discussed.
Brefeld, 1 in a footnote to his account of the life-history of
Coprinus stercorarius, has stated that all the four spores of a
basidium are discharged simultaneously, and that, immediately
after a discharge, small drops are left upon the vacant sterig-
mata and also on the spores. He came to the obvious and
apparently sufficient conclusion that the spores are shot forward
on account of the bursting of the sterigmata and the ejacu-
lation of their contents. However, after studying the discharge
of spores in several species of Coprinus, as well as in Polyporus
squamosus, Psalliota campestris, &c., I find myself unable to
confirm Brefeld's observations. The facts brought forward in
the last chapter 2 afford conclusive proof that the four spores
of a basidium are discharged not simultaneously but successively.
By applying my Method IV. 3 to the examination of a gill
margin (Plate II., Fig. 12) of a ripe Coprinus fruit-body, any one
may observe the successive discharge of the four spores from
scores of basidia in a few minutes. The shooting off of all four
spores usually occupies from about one to several minutes. At the
moment of discharge of the spores from the basidia of Coprinus
comatus, Polyporus squamosus, &c., I have endeavoured to observe
drops on the vacant sterigmata, but without success ; nor, by using
my Method I., 4 have I been able to detect drops on any spores as
1 Brefeld, loc. cit. 2 Under Method IV.
3 Chap. XI. Chap. XI.
148
<
THE MECHANISM OF SPORE-DISCHARGE 149
soon as they have settled on glass immediately after leaving the
basidia. 1
For the purpose of finding out the mechanism of spore-
discharge, a transverse section through the hymenial tubes of
Polyporus squamosus was cut, and the horizontal basidia looked
down upon with the vertical microscope as already described for
Methods I. and V. 2 A particular basidium, bearing four ap-
parently ripe spores, was carefully focussed. After a watch had
been kept for some time, one of the spores suddenly disappeared.
The end of the sterigma left vacant was then seen to be pointed and
entirety devoid of any drop of fluid (cf. Fig. 53, p. 146 ; also Plate I.,
Fig. 3, and Plate III., Fig. 16). The vacant sterigma also appeared
<x> be quite as long and as turgid as the other three still bearing
spores. The basidium did not seem to have altered in volume.
There was nothing to suggest that the sterigma had opened and
discharged a mass of fluid through its very fine neck. The end
of the sterigma, which is only about 0'5 p wide, gave the im-
pression of being closed. Subsequently two further discharges of
spores were observed. There was an interval of a few minutes
between two successive discharges. Again, each sterigma, im-
mediately after discharging its spore, appeared to be pointed at
its end and devoid of any terminal drop of fluid. Even when
three spores had been discharged, I was unable to observe any
collapse of the basidium. All four sterigmata appeared to be
equally turgid. The fourth spore remained on its sterigma for
more than half-an-hour after the discharge of the third and was
not seen to disappear. In several other instances one or two
1 Massee, in his Text-Book of Fungi (London, 1906), says : " In the Hymeno-
mycetes the mature spore is cut off from the apex of its sterigma by a transverse
wall. The sterigma retains its parietal protoplasm after the spore is cut off, and
its elastic wall continues to stretch as the tension due to the accumulation of
water increases. When the tension reaches a certain point, the wall of the
sterigma ruptures in a circular manner just below the septum at its apex ; the
elastic wall of the sterigma instantly contracts and forces its contained water to
strike the apical transverse wall, which is thus thrown off along with the spore
seated upon it." The reader is unfortunately left in doubt as to the authority
upon whom reliance has been placed for these statements. The account of spore-
discharge, however, is similar to that of Brefeld and merits the same criticisms.
2 Chap. XL
150 RESEARCHES ON FUNGI
spores were observed to be discharged from the sterigmata in
precisely the same manner as that described. Similar results were
obtained with Marasmius oreades and Coprinus comatus.
The small size of the basidia and the difficulty of seeing the
narrow neck of a sterigma where it is joined on to a spore, make
it extremely difficult to observe what physical change takes place
at the end of the sterigma at the moment of spore-discharge.
However, after consideration of all the observed facts, it seems to
me that some conclusion as to the mechanism of the process
may be drawn.
The first theory of spore-discharge which we may consider
is, that the four spores are shot off the sterigmata owing to the
latter breaking at their ends and discharging drops of fluid
consisting of cell-sap driven out of the basidium by the contraction
of the cell-wall. 1 I fail to find any facts in favour of this con-
ception. No drops could be detected on the sterigmata or spores
immediately after discharge. The disappearance of the spores did
not lead to any observable collapse of the sterigmata or basidium.
A strong adverse argument may also be derived from the fact
that the spores are discharged successively. A basidium is unicel-
lular. If, when a spore was discharged, the sterigma broke across
and a drop of fluid was forced out, the hydrostatic pressure in
the basidium would be very considerably lessened. There would
be a puncture in the cell. Under such conditions it seems diffi-
cult to imagine how the pressure could be used again for the
successive discharge of the three remaining spores.
It seems to me that the clue to explain the mechanism of
spore-discharge can be obtained from comparative studies in other
groups of fungi. In the Ascomycetes, e.g. Ascobolus, the spores
are evidently driven out of the ascus by the pressure of the cell-
wall upon the cell-sap. The end of the ascus suddenly breaks
open, the ascus collapses, and the eight spores are discharged
simultaneously along with the cell-sap. A similar mechanism is
to be found for Pilobolus and Empusa Muscee. There is, however,
1 We may suppose by analogy with other plant cells that the pressure of the
cell-sap upon the protoplasm and wall of the basidium is due to the process of
osmosis, and amounts to several atmospheres.
THE MECHANISM OF SPORE-DISCHARGE 151
another way in which the hydrostatic pressure may be used as a
driving force. This is illustrated in several Entomophthorinese.
In Empusa Grylli, according to Nowakowski, 1 the wall separating
the conidium from the basidium is double. There is a tiny colu-
mella projecting into the former. When the conidium is ripe,
the two walls separate by mutually bulging in opposite directions
hi response to hydrostatic pressure both in the conidium and the
basidium. In consequence of the bulging taking place very
rapidly, the spore is shot forwards to some distance. It thus
happens that the basidium is not punctured in discharging its
spore, and therefore does not lose any cell-sap. The basidium
merely alters its shape. It becomes slightly enlarged terminally,
whilst doubtless contraction takes place laterally. Probably during
this process the hydrostatic pressure of the cell-sap upon the cell-
wall becomes slightly diminished. We have a process which
we may distinguish as the jerking discharge as opposed to the
squirting discharge of Empusa Muscse and Ascobolus, &c. 2
It appears to me very probable that the four spores are dis-
charged from the basidia of Hymenomycetes by a jerking process
essentially similar to that just described. This hypothesis involves
the assumption of a double wall separating the sterigma and spore,
and that the two walls mutually bulge so as to press against one
another when spore-discharge takes place. That such a double wall
in each sterigma must be present seems to be proved by the fact
that both spore and sterigma are turgid after discharge. The
pointed " tail " of each spore and the pointed end of the sterig-
mata after becoming naked are facts in favour of the idea of a
mutual bulging of the two walls which were in contact. The
hydrostatic pressure in the basidium would be only very slightly
diminished as each spore was shot off and would be available
1 Quoted from Die Pflanzen-familien of Engler and Prantl, who reproduce
Nowakowski's figures. Teil 1, Abteil 1, Entomophthorineae, p. 135.
2 In Bosidiobolus ranarum we have both squirting and jerking processes in
succession. The basidium first breaks across, and the outer end with the spore
is shot away by the squirting process. The spore is then shot off the collapsed
end of the basidium by the jerking process. The spore-wall at the place of
attachment bulges out so as to become pointed. In Conidiobolus utriculosus,
apparently, sometimes the squirting process is used and sometimes the jerking.
See Engler and Prantl, loc. cit.
152 RESEARCHES ON FUNGI
for the discharge of them all. The great difficulty in verifying
this hypothesis is that of observing what happens to the end of
the sterigma at the moment of spore-discharge. However, the
following facts seem to be distinctly in its favour: (1) Successive
discharge of the four spores, (2) absence of drops on the end of
the sterigmata or on the spores immediately after discharge,
(3) apparent closed condition of the sterigmata after ejecting
their spores, and (4) non-collapse of the sterigmata and basidium
as the spores disappear.
CHAPTER XIII
THE SPECIFIC GRAVITY OF SPORES
THE measurements described in this and the following chapter
were made chiefly with the object of testing Stokes' Law.
In order to determine the specific gravity of spores, the heavy-
fluid method was employed. Owing to the minute size of the spores
and' their very slow rate of fall even in water, and also in order
to reduce convection currents to the least possible minimum, it
was found necessary to use a special small chamber with which
to carry out the tests. After several chambers had been tried,
the most suitable one proved to be an ordinary Leitz-Wetzlar
counting apparatus, such as is used for estimating the number of
blood-corpuscles in drops of blood. In the chamber in question
the distance between the cover-glass and the central disc is only
0*1 mm.
The mode of procedure in making the experiments was as
follows : A fresh fungus was obtained, and its pileus was cut off
and placed on a piece of glass or paper, where, in the course of
a few minutes or hours, a spore-deposit collected. Some drops
of the solution to be tested, namely, calcium chloride of known
specific gravity, were then poured into a small beaker. Spore
masses were scraped up from the spore-deposit with a needle
and placed in the solution. This was then stirred vigorously, so
that the spores became well separated and fairly evenly suspended
in it. A drop of the fluid containing the spores was next placed
in the Leitz-Wetzlar apparatus and the cover-glass applied. If
the spores were heavier than the medium in which they were
suspended, they gradually sank and collected on the bottom of
the chamber. If they were lighter, they gradually rose and
collected beneath the cover-glass. The end-result by this means
could usually be determined in a few minutes. Convection currents
'54
RESEARCHES ON FUNGI
are practically reduced to nothing in the chamber, and the spores
had to travel at most upwards or downwards only a distance of
0*1 mm. By focussing and watching an individual spore in the
fluid, one could quickly decide whether it was falling or rising.
The results of the tests for Psalliota campestris, Coprinus
plicatilis, and Amanitopsis vaginata are given in the following
table, where R indicates that the spores rose in the fluid, S that
they sank, and RS that about equal numbers rose and sank
respectively :
.-!? 1*
-S >>G
o^g
Specific Gravity Deterin
inations.
5-C-f
??!!
iPJ
m
3-z
< s
Sp. gr. of CaCl 2 solu-
1-451-441-43
1*41
1-4
1-3551-325
1-305
tions
1-43
1-21
Coprinus plicatilis
B
R
R S
8
S
8
8
s !
Sp. gr. of CaCl 2 solu-
1-5 ]
34 1-32
1-31
1-305
1-293
l-271'OO
tions
1-31
1-2
Psalliota campestris
B
|
R
R
8
8
8
S
S
Sp. gr. of CaCl 2 solu-
j.
1
1-05 1-025 1-015
1-01
1-00
tions
1-02
1-02
Amanitopsis vaginata
R
R
R
S(P)
S
S
Sp. gr. of cane-sugar
1-03
1-025
1-02
1-015
i-oo
solutions
1-02
1-02
Amanitopsis vaginata
B
R
RS
8
S
When fresh spores are placed in water they are turgid and
fully expanded, and present the same appearance as they have
when just about to be liberated from their sterigmata. However,
in solutions of calcium chloride the spores decrease in size. In
many species they become obviously deformed. The spores of
Psalliota campestris in a calcium chloride solution of sp. gr. 1'32
are indented on one side, and the spores of Coprinus plicatilis in
a solution of sp. gr. 1-44 have the shortest of their three axes
(cf. Fig. 55, A, p. 162) reduced to nearly one-half. The decrease
THE SPECIFIC GRAVITY OF SPORES 155
in volume, if such there is, in spores of Amanitopsis vaginata in
a solution of sp. gr. T02 is so small as not to be observable. The
heavy-fluid tests only give us the apparent specific gravity of the
spores. There seems to be little doubt that the decrease in volume
is due to loss of water which passes out from the spores by osmosis
in accordance with well-known laws. Loss of water from the spores
must of necessity increase their specific gravity, for the salts and
other bodies heavier than water must thereby become concentrated.
We can conclude, therefore, that the apparent specific gravity of
the spores in the heavy fluid is greater than the specific gravity
of the spores when fully expanded in water. The tests with the
solutions inform us that the true specific gravity of the spores is
between 1 and T43 for Coprinus plicatilis, between 1 and 1'32
for Psalliota campestris, and between 1 and 1-02 for Amanitopsis
vaginata. In the last-named species the result obtained with
calcium chloride was confirmed by means of a solution of cane-
sugar.
By determining the loss of volume of spores of Coprinus
plicatilis when placed in a calcium chloride solution of sp. gr. 143,
I have been able to calculate approximately the true specific gravity
of the spores in water.
With the aid of a Poynting Plate Micrometer the spores were
measured with a considerable degree of accuracy. Ten long, ten
short, and ten intermediate axes were measured, each measurement
being made on a different spore. The average size of the spores
was thus found to be
In water 12-54 x 10-33 X 814
In CaCLj solution, sp. gr. 1-43 . 11-76 x 10-18 x 4-5
By multiplying the three axes together we can calculate that on
the average for each spore
(volume in water) : (vol. in CaCl 2 solution, sp.gr. 1-43) : : 1054 : 538.
We may conclude, therefore, that when a spore is taken from
water and placed in the calcium chloride solution, its volume is
approximately halved.
Now, it may be shown that
(l x)vs + xvs" = vs'
156 RESEARCHES ON FUNGI
where x represents the fractional loss of volume in the heavy fluid,
v the volume of the spore in water, s the apparent specific gravity
of the spore in the heavy fluid, s' the true specific gravity of the
spore in water, and s" the specific gravity of water itself.
Since = |, s=l*43, and s"=l, we find that s'=l'215, or the
true specific gravity of the Coprinus spores in water is approxi-
mately 1-21.
In the case of the Mushroom, owing to the spores becoming
indented on one side, the exact loss of volume of the spores in a
calcium chloride solution of sp. gr. 1-31 could not be measured
directly. However, it was estimated by inspection as being from
about one-third to one-half of the volume in water. On this
assumption we may calculate from the equation already given that
the specific gravity of Mushroom spores is approximately 1*2.
' The Amanitopsis spores did not show any appreciable con-
traction in the calcium chloride solution or cane-sugar solution
of sp. gr. 1 - 02. Since we have already found that the real specific
gravity of the spores in water must lie between 1 and 1*02, we
may take it that the real specific gravity is approximately 1*02.
This approximation must certainly be correct to within 1 per
cent, of the actual specific gravity.
Another method for estimating the specific gravity of spores
is that of measuring the rates of fall of the spores in air and in
water. The data so obtained are then used in the following
equation, which can be deduced from Stokes' Law which must be
assumed to be true :
v'^p-I^n
v p M'
where v' is the velocity of the fall of spores in water, v the velocity
of fall in air, p, the viscosity of air, p the viscosity of water, and p
the specific gravity of spores.
A counting apparatus, with a chamber 1 cm. square above and
below and 0*2 mm. deep, was used for estimating the rate of fall
of the spores in water. The chamber was filled with water holding
spores in suspension and covered with a cover-glass. A microscope
was then turned into the horizontal position and the counting
apparatus clamped down to the now vertically-placed stage. The
THE SPECIFIC GRAVITY OF SPORES 157
convection currents in the chamber, although not entirely absent,
appeared to be negligible. In the case of Coprinus plicatilis, ten
spores were carefully timed in falling through a field of 1-6 mm.
in width. On the average each spore took 2 mins. 57 sees, to
fall this distance. The velocity of the fall of the spores in water
was thus found to be 0*00090 cm. per second. The velocity of
fall of the spores in air was found by finding the time required
for them to fall vertically through a distance of 4-55 mm. from
pieces of gills placed in a small compressor cell. 1 The speed was
found to be 0-429 cm. per second.
Putting v' = 0-0009, <y = 0'429, ^ = l-8xlO- 4 , and /*' = l-2x 10" 2 ,
we get p, the specific gravity of the Coprinus spores, = 1-16.
With Mushroom spores it was found that v' 0-00025 and
v = 0-13, whence p = 1-15.
Both results are within 6 per cent, of those obtained by the
other method. The present method seems to me to be less
reliable than the first on account of its indirectness and the
assumptions involved. Stokes' Law was assumed to be true : the
spores were not spherical. Possibly the errors in estimating the
rates of fall of the spores in water are quite appreciable. Never-
theless, the result may be correct to within 10 per cent.
If we take the results given by the heavy-fluid method to be
fairly reliable, we may conclude that the specific gravities of the
spores are as follows : for Coprinus plicatilis 1*21, for Psalliota
campestris 1*2, and for Amanitopsis vaginata 1*02. The spores
of the last-named species are much lighter than those of the other
two. This is probably due to the very large amount of oil which
the spores of Amanitopsis contain. The oil is certainly a very
light constituent of each cell, for, when a spore is falling in water,
the large oil mass, as seen with the horizontal microscope, occupies
the highest position possible. On account of the spores of
Amanitopsis vaginata having about the same specific gravity as
water, it was not found possible to measure the rate of their fall
in that medium. Their motion was so slow that even minute
convection currents proved to be a serious source of error in making
the measurements.
1 Vide infra, Chap. XV.
CHAPTER XIV
THE SIZE OF SPORES POYNTING'S PLATE MICROMETER
EACH species produces spores of a definite shape and size. The
spores vary in size about a mean, doubtless in accordance with the
now well-known laws of continuous variation. The variations as a
rule are within fairly restricted limits, so that fungus spores, when
observed with a microscope, appear to resemble one another very
much as do eggs laid by a fowl. By measuring the diameters of
twenty-five spores of any fruit-body, one can obtain an average
size which is correct to within a very small percentage of the
real average for all the spores. It must not be assumed, however,
that all the individual fruit-bodies of a species have spores of
the same average size. Thus, for instance, three specimens of
Amanitopsis vaginata, obtained from the same wood on differ-
ent days, possessed spores with an average diameter of ll'Go /A,
10-87 n, and 10-19 //, (Fig. 55, B, C, D, p. 162). It is not sur-
prising that the spore sizes for species as given by systematists
often disagree.
For the purpose of measuring spores rapidly and accurately I
have made use of Poynting's Plate Micrometer, 1 a simple and exact
piece of apparatus which should come into general use in all inves-
tigations where it is necessary to measure the sizes of numerous
small bodies. Since it seems that I am the first to apply the Plate
1 The Plate Micrometer with which I worked was Professor Poynting's
original instrument. My thanks are due to him for kindly permitting me to
use it in his laboratory. It was exhibited at an Optical Convention held in
London four years ago. In the Proceedings of the Optical Convention, No. 1, Lon-
don, 1905, a one-page account of the principle of the micrometer is given, but this
would be of little use to any one wishing to understand how the measurements
of spore dimensions were made. Professor Poynting has informed me that he
has not yet published an adequate description of the Plate Micrometer as applied
to the microscope, but he has consented to my attempting to show how the
instrument may be used in practice.
.58
THE SIZE OF SPORES 159
Micrometer in a biological research, a brief description of it here
will not be out of place.
The apparatus is provided with a stand, Plate IV., Fig. 26, st,
attached to which is a horizontal arm, a, bearing at its end a vertical
scale, sc. The scale is divided into fifty parts, with the zero at the
top. A carefully prepared plate of glass, 6 mm. thick, p, with
parallel upper and lower faces, is attached to a horizontal rod, r r
which is fixed to the stand so that it can be rotated about its axis
by means of a lever, I. The end of the lever carries a small frame-
work in which is placed a piece of glass. On the latter is scratched
a fine line parallel to the arm of the lever. The line serves to
indicate the position of the lever on the scale. The microscope
is provided with a mechanical stage. It also has a slot, si, in
the tube above the objective, of such a size that the glass plate can
readily be inserted into it. The eyepiece contains a transverse silk
thread.
When the apparatus is about to be used, the glass plate is
inserted into the slot so that it becomes entirely enclosed in the
microscope tube, which, however, it does not touch. The eyepiece
is then rotated until its silk thread comes to be parallel to the
rod, r, bearing the glass plate.
The scale, sc, is calibrated as follows. The lever is first raised
until the line in the terminal framework exactly crosses the zero of
the scale. A stage micrometer is then placed on the microscope
stage so that its dividing lines are parallel to the thread in the eye-
piece. By using the mechanical stage one of the micrometer lines
is made to coincide with the thread of the eyepiece. The lever is
then depressed. This causes the glass plate to rotate slightly. As
one looks down the microscope, the micrometer line appears to move
parallel to itself away from the eyepiece line. By depressing the
lever far enough, one can make a second stage micrometer line
coincide with the eyepiece line. Let us suppose that the distance
between the two micrometer lines is 10 //,, and that the lever has
been moved downwards through twenty-six divisions on the vertical
scale, it is then clear that each scale division has the value /*.
13
By making ten measurements between ten successive divisions of the
i6o
RESEARCHES ON FUNGI
stage micrometer, one can obtain a very accurate value for each
division of the plate micrometer scale.
When the scale has been calibrated by the method just described,
one proceeds to measure the size of spores. These are mounted in
water on a glass slide and covered with a cover-glass in the usual
way. The lever is placed at zero. One then finds a spore with the
axis to be measured directed at right angles to the eyepiece line. 1
Let us suppose that one wishes to measure the long axis. With the
mechanical stage one moves the spore so that one end of it just
touches the eyepiece line (Fig. 54). One then depresses the lever
from the zero of the scale, and as one
does so the spore appears to move
across the eyepiece line from left to
right, until finally it comes to touch it
with its other end. At this point one
ceases to depress the lever and reads
off the number of divisions on the scale
through which it has been moved. By
measuring twenty-five spores in this
"V. ^ b ^ a T good aver-
age on the scale for the dimensions
required. Since the actual value or a
^ micrometer gcale diyision hag
previously been found by calibration, the dimensions of the spores
can readily be calculated.
The advantages of the apparatus are : (1) Its optical soundness
each division on the vertical scale has the same value; (2) the
apparatus is entirely detached from the microscope, so that, when
the lever is moved, the microscope cannot be shaken in any way ;
(3) the accuracy with which the scale can be calibrated ; (4) its
simplicity ; (5) the speed and ease with which large numbers of
observations can be made with it.
The range of variation in the sizes of spores may be gathered
1 With the addition of a rotating stage one could place any spore with its axis
in the desired direction. My microscope, unfortunately, was without this refine-
ment. There is, however, very little difficulty in finding as many spores as one
requires with their axes in the right direction.
r b, ^ySTSS.*; S
Micrometer. By depressing the
lever the spore appears to move
across the eye-piece line EE from
position A to position B.
THE SIZE OF SPORES 161
from the following example, which gives the plate micrometer scale
figures obtained for the diameters of 100 fresh spores of Amanitopsis
vaginata (Specimen III.) measured in water :
41-0
43-0
40-1
45-5
40-7
41-3
40-8
47-5
38-5
42-7
39-5
41-5
39-5
3(5-0
43-6
43-0
38-6
40-2
43-1
39-0
40-0
36'5
43-4
42-0
47-0
42-7
37-4
38-0
400
41-8
45-0
38-0
38-0
39'5
40-7
36'8
44-7
36-0
45-0
43-0
40-2
455
39-2
40-8
43-5
42-5
39-8
43-4
39-8
39-4
42-8
41-5
39-0
44-0
42-3
39-7
39-8
48-0
41-4
46-2
35-6
38-0
38-7
41-0
43-4
38-2
43-0
39-5
40-4
36-1
40-8
39-4
40-0
41-0
40-5
36-1
40-0
41-0
42-1
41-3
410
38-4
42-0
43-6
40-7
39-2
40-5
38-0
38-1
41'0
41-6
42-5
41-4
40-5
40-8
45-4
43'9
40-8
39-4
36-6
407-5 404-3 401'5 413'9 422'6 404'9 408'5 412'4 407'8 407-1
,The average scale measurement for the spore diameters of 100
spores was found to be 40*905. The calibration figures for ten suc-
cessive distances of 10 ^ each on a stage micrometer were as
follows : ! 34-5, 36-1, 35-0, 351, 36-0, 34-5, 34-5, 35*4, 36'0, 34-5, whence
it was calculated that yn = 3'51 plate micrometer scale divisions. The
average diameter of 100 spores, therefore, = =11-65 M.
3"o 1
The Table on page 162 gives some of the results of measurements
with the Poynting Plate Micrometer. Each measurement given
is the average of 25 or 50 measurements of 25 or 50 spores respec-
tively. The last column gives the value /l n g axis x short axis.
Illustrations of all the spores in the Table are given in
Fig. 55.
From the Table the general range in size of the spores of
Agaricineoe may be gathered. 2 The very large spores of Coprinus
plicatilis are about twenty-two times the volume of the very small
spores of Collybia dryophila. In all cases, however, and this
may be stated quite generally for the Hymenomycetes, the spores
are so small that they must fall in the manner indicated by Stokes'
Law, i.e. almost immediately after liberation (within a very small
1 The differences between these readings are due to errors in the construction
of the stage micrometer, and not to any want of delicacy on the part of the Plate
Micrometer.
2 The largest spores of any known Agaric are those of the exceptional Coprimts
gigasporus, which measure 28-30 x 14-16 ^. G. Massee, "A Revision of the Genus
Coprinus," Ann. of Bot., vol. 10, p. 123.
L
1 62 RESEARCHES ON FUNGI
fraction of a single second) they must fall without acceleration at
a uniform speed. The size of the spores is also such that this
Species.
Lon? Axis
in p.
Short Axis
in ju.
Geometrical
Mean of the
Two Axes
in M .
Collybia dryophila
5-44
323
4-2
Pluteus cervinus .
5-95
4-57
5-2
Paxillus involutus
7-48
4-88
6-0
Psalliota campestris :
Grown on a bed, I. .
7-17
5-41
6-25
,. II-
7-26
5-35
6-25
,! ni. .
7-32
5-64
6-4
From a field, IV.
9-7
5-80
7-4
Marasmius oreades
9-5
5-6
7-4
Boletus badius .
12-8
4-29
7-4
Amanita rubescens
9-38
6-53
7-8
Galera tenera
10-47
606
7-96
Russula emetica .
8-82
7-50
8-2
Polyporus squamosus .
Coprinus comatus
Amanitopsis vaginata, I.
14-6
12-55
10-
5-13
7-48
19
8-7
9-8
10-19
II-
10-87
1087
III. .
11-65
11-65
Coprinus plicatilis
12-9 10-7 7-9
11-8
uniform speed is only about 0-5-6 mm. per second. The spores,
therefore, are so tiny that even the slightest air-currents can
A BCDEFCH
*!
M N
tit
R
t I
o lou a.ou,
FIG. 55. The average spores of individual fruit-bodies of various species of
Hyruenomycetes. A, Coprinus plicatilis; B, C. and D, three individuals of
Amanitopsis vaginata; E, Coprinus comatus ; F, Russula emetica; G, Poly-
porus squamosus ; H, Galera tenera ; I, Amanita rubescens; J, Boletus badius;
K, Marasmius oreades; L, M, N, and 0, four individuals of Psalliota campestris;
P, Paxillus involutus ; Q, f-luteus ceroinus ; R, Collybia dryophila.
carry them long distances away from the fruit-bodies upon which
they have been developed.
THE SIZE OF SPORES 163
The difference between the average size of the spores for
individual fruit-bodies is indicated by the results obtained for
Psalliotct campestris and Anumitopsis vaginata. The field Mush-
room probably belonged to a variety distinct from that of the
cultivated ones. It was characterised not only by relatively iriuch
longer spores but also by much deeper gills.
The average diameter of the spores for Specimen III. of
Amanitopsis vaginata was 14'3 per cent, larger than the average
size for Specimen I. It is clear from this instance that fruit-
bodies of the same species may have considerable individual
variability in regard to the average size of their spores.
CHAPTER XV
THE RATE OF FALL OF SPORES AND STOKES' LAW APPENDIX
So long ago as 1851 Stokes 1 published a paper called "On the
Effect of Internal Friction of Fluids on the Motion of Pendulums."
In the course of a mathematical treatment of his data, he deduced
an equation expressing the relations between the density of a
falling microscopic sphere, the size of the sphere, the velocity
of its fall, the density of the fluid through which it may fall, and
the viscosity of the fluid. The equation represents what is known
as Stokes' Law : 2
where V = the terminaljvelocity,
p = the density of the falling sphere,
<r=the density of the medium,
g = the acceleration due to gravity,
a = the radius of the falling sphere,
p. = the viscosity of the medium.
For more than forty years this equation remained untested
for the fall of small particles in air and other gases. This, no
doubt, was due to the technical difficulties of procuring microscopic
spheres of known density and size, and of dropping them through
gaseous media in such a manner that their rate of fall could be
measured. The verification of Stokes' Law by means of such
experiments has recently become of some importance owing to
the necessity of assuming it in investigations upon the electronic
charge as made by J. J. Thomson 3 with the cloud method.
The only evidence hitherto 4 adduced to show that Stokes' Law
1 G. Stokes, Camb. Phil. Trans., vol. ix., Part II., p. 8.
Cf. the Appendix to Chap. XVII.
3 J. J. Thomson, Phil. Mag., December 1898; December 1899.
* This was written in 1907. Since then Zeleny and M'Keehan have recorded
experiments with lycopodium powder. Vide the Appendix.
164
THE RATE OF FALL OF SPORES
165
holds for the fall of small spheres in air appears to be that obtained
by J. J. Thomson, whose value of the electronic charge, obtained
by Wilson's 1 cloud method involving the assumption of Stokes'
Law, was found to agree with the generally accepted value of the
electronic charge as calculated by application of the kinetic theory
FiG. 56. Amanitopsis vayinata. Kelations of the spores to the fruit-body. A,
transverse section through two gills showing the hymenium, A, from which
basidia are projecting. The arrows indicate the paths of spores which, after
discharge from their basidia, have fallen in still air. Magnification, 15. B,
vertical section through the hymenium and subhymenium. p, paraphyses :
a-e, basidia ; a, with rudimentary spores ; 6, with ripe spores ; c, with two
spores discharged ; d, with three spores discharged ; c, with all the spores
discharged : , the subhymenium. Magnification, 370. C, isolated basidium
with two spores discharged showing mode of attachment of spores to their
sterigmata. Magnification, 1110. D, discharged spore. Magnification,
1110. E, basidium with rudimentary spores. Magnification, 1110.
of gases. This verification of the applicability of Stokes' Law is,
of course, very indirect.
It seemed to me of interest to attempt to determine experi-
mentally whether the spores of Hymenomycetes fall in accordance
with Stokes' Law. It was hoped that, by making three separate
measurements of the specific gravity, size, and velocity of fall of
1 C. T. R. Wilson, Phil. Trans., 1897.
166 RESEARCHES ON FUNGI
the spores, one might obtain a direct test. It was also thought
that an actual determination of the rate of fall of spores would
throw light upon the distribution of bacteria, spores, and other
organic particles in air, and also help to explain fruit-body structure.
A considerable amount of preliminary experimentation was
undertaken, during which observations were made upon the rates
of fall of spores of various shapes and sizes in still air. The spores
of Amanitopsis vaginata were then chosen as material for a critical
test of Stokes' Law for the following reasons : (1) They are spherical
except for a tiny " tail," and smooth-coated (Fig. 55, A, B, and C,
p. 162). (2) They are comparatively large, so that one can measure
their diameters, which are about 10 /* wide, very
accurately with the Poynting Plate Micrometer.
(3) Their density is almost that of water, and
can be measured within 1 per cent, of ac-
curacy. 1 (4) They could easily be procured, for
the fruit-bodies of Amanitopsis vaginata came
up in sufficient abundance in Sutton Park,
which was not many miles from the laboratory.
FIG. 57. Diagram to Fresh fruit-bodies (Plate IV., Fig. 30) could be
obtained throughout August and September,
placed in the com- during which time the critical experiments were
pressor cell. The gills
are directed vertically made. The relations of the spores to the fruit-
body are shown in Fig. 56.
An experiment to measure the rate of fall of Amanitopsis spores
was carried out in the following manner. A fresh fruit-body was
obtained from the woods and used within a few hours of being
gathered. Due care was taken in carrying the fruit-bodies to the
laboratory, upon reaching which they were immediately placed
upright in a wet sand-bath and covered over Avith a large bell-jar.
A small piece of the pileus, including portions of three gills, was
then dissected out (Fig. 57) and placed in a compressor cell in the
position shown in Fig. 58, p. To prevent the falling spores from
drying, two soaked pieces of blotting-paper or cotton-wool, 6, and a few
drops of water, w, were then added. Upon the cap being adjusted, the
piece of fungus became fixed by slight compression and hermetically
1 Vide Chap. XIII.
THE RATE OF FALL OF SPORES
167
FIG.
sealed in the disc-shaped chamber of which the base and top con-
sisted of glass. The compressor cell was then placed in the vertical
position (i.e. with the glass plates vertical) and clamped by one end
to a stand. By this means it was possible to cause the gills to look
vertically downwards in the natural manner. Thus enclosed in the
chamber, the gills continued to rain down spores for some hours.
In order to observe the
falling spores, a special micro-
scope on a stand of simple
construction l was employed.
The microscope tube was placed
in the horizontal position
(Plate IV., Fig. 29), and could
be screwed upwards and down-
wards by means of a rackwork
on the stand. The amount of
rise or fall could be read off
on a vertical scale to which
a vernier was attached. The
microscope tube was arranged
at such a height and at such a
distance from the chamber as
to focus a field (shown by the
dotted ring in Fig. 58) immedi-
ately below the gills where the
spores were falling. To illu-
minate the microscope, diffuse
daylight, obtained from the
glass roof, was reflected into
the tube by means of a plane mirror (Plate IV., Fig. 29). The
observations were made in a basement room where the temperature
was very constant for considerable intervals of time.
The horizontal microscope was provided with a Ramsden eye-
piece. Three fine silk threads were attached to it so as to cross the
field of view. The distance between the extreme threads, as seen in
the field of view when the microscope was focussed, was 4'55 mm.
1 Made by Pye & Co.
58. The compressor cell used for
measuring the rate of fall of spores. A
section of the cell is shown above : the
chamber c can be varied in size by rais-
ing or pressing down the cap. g, glass.
Below is shown the cell when in use. ;<,
a piece of pileus with gills looking down-
wards (c/. Fig. 57); 6, b, wet blotting-
paper or cotton-wool; w, a free drop of
water. The dotted circle shows the field
of view of the horizontal microscope when
focussed just beneath the gills. The
three arrows show the courses of three
spores falling from between the gills and
crossing the field. The horizontal lines
in the latter are produced by three silk
threads in the Ramsden eye- piece. Actual
size.
i68 RESEARCHES ON FUNGI
(Fig. 59), while above and below them there was a further space
of 0*5 mm. The magnification, namely, about 25 diameters, was
obtained by using a No. 1 Leitz objective and extending the draw-
tube.
On viewing a field just below the gills, spores can be seen as
distinct but only just visible, very minute, dark objects, steadily
crossing the field in a vertical direction, apparently from below
upwards. Every spore so falling is not in focus, but, when the fungus
material is in good condition, spores in focus come into view at least
^, i every five seconds. Often one can see
three, four, or five spores in focus at the
Is same time.
The spores fall vertically downwards
(apparently upwards). In the small cham-
ber employed, convection currents are re-
duced to a minimum and produce no
FIG. 59. The field of the
horizontal microscope, apparent disturbing effects on one s obser-
apart ^ThT^ppCT^nd vations. Doubtless, there are very slow
lower horizontal threads a i r . currents i n the chamber, but I have
in the eye-piece when
seen in the field of view no reason to suppose in my critical experi-
was 4-55 mm. . .
ments with the large spores of Amamtopsis
that they produced an error in the record of speeds of 2 per cent.
Even with the small spores of Collybia dryophila, which often
take eleven seconds to cross the field, the direction of the paths
of fall is vertical and there is practically no swerving from the
course.
The records of the velocity of fall of the spores whilst crossing
the field of the horizontal microscope were made with the aid of
a large drum, which was driven by electricity and provided
with a delicate regulator (Plate IV., Fig. 29). A recording
fountain-pen produced a continuous spiral line upon the paper
as the drum rotated. To the pen was attached an electric
tapping key, which could be placed in a convenient situation
near the microscope. When the knob of the contact apparatus
was depressed, the pen immediately deviated from its course upon
the paper.
When the apparatus was ready, the drum was set going and the
THE RATE OF FALL OF SPORES
[69
fall of spores watched through the microscope. As soon as a spore
clearly came into view at the bottom of the field, it was followed
1
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0. Amanitopsls vayinata. Pai
te of fall of a hundred spores
mpressor cell containing a fre<
which the pen moved relativ
e time-record made with the h
e speed of the drum. The wh
te of fall of the spores was fou
r
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with the eye. When it crossed the first line of the field, a con-
tact was made with the finger by depressing the key. Similarly,
RESEARCHES ON FUNGI
second 1 and third contacts were made as the spore crossed the
second and the third lines
respectively. Thus for
the fall of each spore the
pen deviated three times
from its normal path on
the paper of the drum
(Figs. 60 and 61). The
fall of about 100 spores
was recorded in this way
as rapidly as possible, the
entire record usually be-
ing completed in less than
fifteen minutes. A time
record of ten seconds was
always made on the drum
before and after each
series of observations by
means of a chronometer
ticking half-seconds. The
drum kept up a very con-
stant peripheral velocity,
which was usually T16
cm. per second. When the
records had been made,
they were measured off
on the drum by means of
a steel tape, added up, and
the average taken. By
measuring the distance
run by the drum in ten seconds, the speed of the drum could be
determined. The average length of time represented by the average
1 There was no absolute necessity to record the passing of the middle line by
a spore, but it was found convenient to do so for the purpose of distinguishing
the individual spore-records from one another on the drum. Every effort was
made to make the first and third contacts precisely at the times the upper and
lower lines were being crossed ; but the second contact, being of quite secondary
importance, was naturally not always recorded so accurately. The middle line
was 2'22 mm. from the upper line and 2'33 mm. from the lower line.
I
C
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12
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. Ptalliota ca
ntained wet bL
e average rate
^ O H
i
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i
k
O
THE RATE OF FALL OF SPORES
171
record of the spores on the drum could then be calculated. Since
this average time was that required for the spores to fall through
a distance of 4'55 mm., the average velocity of fall of the spores
could be calculated.
The following figures give the drum records of 200 spores of
Amanitopsis vaginata. 1 The first series of 100 took about twelve
minutes to record. After an interval of forty minutes, the second
series of 100 was made. The drum records, measured on the drum
by means of a steel tape, are given in centimetres.
SERIES I. SERIES II.
0-85 0-80 0-85 O95 0'88
0-70 1-05 0-85 0-74 0'85
0'9o 0-86 0-87 0-97 0'89
1-03 0-91 0-75 0-68 0'84
0-95 0-89 0-89 0'93 0-65
0-88 0-88 0-75 0-75 0-85
0-95 0-90 0'78 0'91 0'75
0-96 0-76 0-99 076 0'80
0-84 0-80 0-88 0'90 0'89
0-80 0-81 1-00 0-80 0-74
0'71 0-88 0-82 0-95 0'90
0-80 1-05 0-75 0-84 0'76
0-85 0-95 0-85 0'75 0'82
1-01 0-94 0-99 0-86 0'77
0-92 0-89 0-86 0'99 0'78
0-95 0-94 0-75 0'87 0-76
0-84 0-85 0-94 0'82 0'84
0-90 0-75 0-79 0'79 0-82
0-96 0-89 0-90 0-93 O90
0-99 0-85 0-83 0'80 0'94
0-84 0-80 0-92 0'89 O94
0-93 0-85 0-68 0'92 0'88
0-80 0-94 0-94 0'99 O64
0-92 0-80 0-92 0-91 0'89
0-73 0-94 0-89 0'78 0'75
0-95 0-84 0-89 0'88 0'92
0-82 0-99 '0-85 0'81 0'72
1-08 0-90 0-85 0-92 0'96
0-84 0-89 0-82 0'85 0'74
0'93 0-65 0-85 0'80 0'94
0-84 0-89 0-85 0'84 O92
0-96 0-85 0-75 0'85 1'04
0-97 0-93 I'OO 0-79 0'91
1-04 0-91 0-81 0-94 0'89
0-90 0-89 0-97 0-85 0'85
0-99 0-95 0-90 0'91 0'95
1-00 0-90 0-85 0-74 0'60
0-91 082 0-90 0-94 0'88
0-77 0-87 0-95 0'90 O95
1-00 0-90 0-90 0-90 0-81
17-33 17-75 17-68 17-54 16-32
18-73 17-41 16-90 16-86 17'29
Sum of totals . . 17'33
Sum of totals . . 18'73
17-75
17-41
17-68
16-90
17-54
16-86
16-32
17-09
Grand total . . . 86'62 cm.
Grand total . . . 87*19 cm.
Average distance on drum in Series I.
Average distance on drum in Series
= 0-8662 cm.
II. = 0-8719 cm.
Average speed of drum = l-16 cm. per
Average speed of drum = 1 -16 cm. per
second.
second.
Hence average time of fall of each
Hence average time of fall of each
spore in falling through a field of 4'55
spore in falling through a field of 4'55
mm. = 0-747 seconds.
mm. = 0-752 seconds.
4'55
Hence average velocity of fall =
Hence average velocity of fall= -^..^
U* < DZ
= 6'09 mm. per second.
= 6*05 mm. per second.
Hence average velocity for both Series together = 6-07 mm. per second.
Specimen I. in Chap. XIV.
172 RESEARCHES ON FUNGI
The Table on the next page gives a summary of the data obtained
for testing Stokes' Law with falling spores of Amanitopsis vaginata.
The velocities given are the average velocities of 200 spores in
Specimen I., of 100 in Specimen II., and of 50 in Specimen III. The
densities are certainly correct to within 1 per cent. 1 The diameters
are the average diameters for at least 50 spores, these being spherical.
The measurements were made with a Poynting Plate Micrometer in
the manner already described. The spores of Specimen I. were
those collected at the bottom of the compressor cell whilst observa-
tions on the fall of some of them were being made. The spores of
Specimen II. were obtained from another part of the fruit-body from
which the piece had been dissected out for velocity observations in
the compressor cell. The spores of Specimen III. 2 were those col-
lected from the piece of fungus used for the velocity records, but
collected from it immediately after these had been taken. It is
clear, therefore, that I was unable to measure the diameters of
exactly those spores for which the velocity of fall had been recorded.
This is a defect in my method. However, the defect seems to me
of little importance, for it was found that any 50 spores, taken at
random from any part of a single fruit-body, have the same average
size. In order to obtain the average size of the spores of which
the velocity had been recorded, it was therefore only necessary to
measure the average size of any 50 spores obtained from the fruit-
body.
In making calculations with Stokes' equation, the viscosity of
air 3 was assumed to be 1'8 x 10~ 4 and its density negligible compared
with that of a spore. The value of g was taken as 981.
From the Table it is clear that the figures obtained by
observation for the rate of fall of the spores are of the same
order of magnitude as those demanded by Stokes' Law. How-
ever, the Law is not confirmed in detail, for as an average for the
three cases it was found that the actual velocity of fall of the
spores was 46 per cent, greater than the calculated.
1 Vide Chap. XIII.
2 For actual measurements, vide Chap. XIV.
8 1-8 x ID'* is the value usually taken for dry air at room temperatures. The
effect of moisture is to very slightly reduce the viscosity.
THE RATE OF FALL OF SPORES
A manitopsis Vaginata
173
Chamber, containing soaked blotting-paper or cotton-wool and free water below,
closed for half-an-hour before observations for velocity were taken. Field of
microscope close under gills.
Jfjtlliiif jffitjlk
nC!8~2iifc -3-5S a , -=; P^-
llplil >2 ! -81151 1, i HIS
-rv-.Sa rt cs ,? 2 jJ3 u * ' 5^5
1I"Irl=i 11= : l:t|J : lls a
3^1fsl "5* : 3*5 s I: s
I
I
Specimen I. 1'02 11 "65. 6 "07
Specimen II. 1-02 10'19 ! 4'85
Specim en III. I 1 '02 1 10 -87 j 5 1 1
4'14
3-21
3-64
47
51
40
14-0
12-52
12-9
-16-8
-18-6
-15-0
It is difficult to explain why the observed velocities of fall
should be nearly 50 per cent, greater than that demanded by
Stokes' Law. However, perhaps the explanation has some con-
nection with the fact (to be discussed more fully in the next
chapter) that, even in an apparently saturated chamber, the
spores in falling even such a small distance as 5 mm. lose a
certain amount of water. It was found that after leaving the
gills, the rate of fall of the spores slightly decreases. Further
experiment showed that this was due to the contraction in the
volume of the spores consequent on drying up. 1 It has been
suggested to me by Professor Poynting, that the loss of water
by a spore during its fall might lead to an evaporation pressure
of such a kind that the spore would be forced more quickly down-
wards than would be the case if no loss of water were taking
place. Owing to the impossibility of employing perfectly dry
spores in my experiments, there seems to be no way at present
to test this hypothesis.
That the speed of fall on the average was found to be 46 per
cent, greater than that given by Stokes' Law may possibly be
accounted for by surface slip. With very minute particles Stokes
1 Vide infra, Chap. XVI.
174 RESEARCHES ON FUNGI
has calculated that the maximum effect of slip is to increase the
terminal velocity by 50 per cent. Therefore, if we assume that
the slip actually takes place, the discrepancy between observation
and theory would be fully accounted for. It seems, however, that
the spores are not small enough to permit of our assuming slip
to the extent required.
The most serious objection to my method for testing Stokes'
Law seems then to be that it has so far been found impossible
to get the spores to fall with a quite constant speed in an
apparently saturated chamber. Now the spore diameters were
measured when the spores were in water, i.e. when fully turgid,
just as spores are upon the sterigmata immediately before their
fall. In order, therefore, to observe the fall of the spores when
they were in as turgid a condition as possible, the two precautions
(1) of placing the field of the microscope immediately under the
gills, and (2) of saturating the chamber so far as possible with
water-vapour, were taken. If the velocity of the spores could
have been measured immediately they left the sterigmata instead
of when they came into view beneath the gills, probably it would
have proved even greater than that recorded.
All the measurements for density, size, and velocity of the
spores could be made with great exactness. It seems to me
most unlikely that the large discrepancy between theory and
observation can be due to errors in these measurements. Unless
loss of water from the spores in some way is capable of accel-
erating their rate of fall, for the present it would seem as though
the spore-fall method of testing Stokes' Law shows that the
actual velocity of fall of spheres about 10 /A in diameter is some
50 per cent, greater than the Law demands.
The appended Table, giving the results of observations upon
the rates of fall of spores of various species, was compiled before
the tests for Stokes' Law were made. The air in the chamber of
the compressor cell was not saturated and simply contained the
required piece of fungus. The field of the microscope was
usually near the gills. The rates of fall of spores of a single
fruit-body, as the spores dry up, gradually decrease after the spores
have left the gills. The figures given in the Table serve merely
THE RATE OF FALL OF SPORES
175
to show the speed of fall of the spores at a certain distance from
the gills in the unsaturated air of the chamber. If V be the
velocity of a spore when fully expanded by osmotic pressure,
i.e. just after liberation, and V be the velocity of the same spore
when it has dried up, then the velocities given in the Table lie
between V and V. The value of V, as further experiments have
shown, may be as much as 3V. It will doubtless be different
for each species, but it is evident, from results given in the
Tables in the next chapter, that up to 60 per cent, should be
added on to the velocities given in the present Table in order
to obtain approximately the true rate of fall of the fully turgid
spores of which the dimensions are given. On the other hand,
if, one wishes to calculate the velocity of the spores when dried
up, as they must often be in nature within one or a few minutes
of leaving the fruit-body, one must subtract up to 60 per cent,
of the velocities determined.
Species.
Spore Dimensions in p.
Velocity of
Fall in mm.
per Second.
Loner Axis.
Short Axis.
Collybia dryophila
5-44
3-23
0-49
Pluteus cervinus
5-95
4-57
0-67
Psalliota campestris :
Grown on a bed, I. .
7-26
5-35
1-06
II.
7-32
5-64
1-30
From a field, III.
9-7
5-80
1-61
Polyporus squamosus .
Boletus badius .
14-6
12-8
5-12
4-29
1-03
1-09
Paxillus involutus
7-48
4-88
MO
Boletus felleus .
1459
3-78
1-22
Marasmius oreades
9-5
5-6
1-34
Russula emetica .
8-82
7-50
1-64
Amanita rubescens
9-38
6-53
1-54
Galera tenera
10-47
606
2-13
Amanitopsis vaginata
9-64
9-64
2-95
Coprinus comatus . | 12-55
7-48
3-96
Coprinus plicatilis
12-9 107
7-9
4-29
It was found possible to measure the rates of fall of individual
spores over longer distances than 4'55 mm. in the following
manner. A field just below the gills in the compressor cell was
focussed with the horizontal microscope. When a spore crossed
the upper line, a drum contact was made by depressing the knob
1 76 RESEARCHES ON FUNGI
of the tapping key with the left hand. The microscope was then
lowered with the right hand by means of a rackwork on the
stand so that the spore was still kept in view. When the field
arrived at the bottom of the compressor cell after having been
lowered in this way for about 8 mm., the spore crossed the lower
line of the field, whereupon a second drum contact was made.
The time of fall could therefore be calculated from the drum
record in the usual way. The distance of fall could be deter-
mined by adding to the distance between the upper and lower
lines of the field, namely 4'55 mm., the distance through which
the microscope had been lowered. The latter was found in each
case by reading a vertical scale which was situated on the
microscope stand and provided with a vernier. From the time
and distance data thus obtained the velocity of fall could be
calculated at once.
Fifty measurements with the spores of Boletus felleus were made
in the manner just described. The average observed distance of
fall was 12'05 mm. and the average time required to fall through
it 10'57 seconds. Hence, the average velocity of fall through
12-05 mm. below the gills was 114 mm. per second. Doubtless by
this method the rate of fall of small particles might be measured
through greater distances than 12 mm.
Whilst measuring the rates of fall of spores the magnification
was kept as low as practicable, so that the observed distance of
fall should be as large as possible. Under those conditions the
spores were seen merely as just visible specks, the shape of which
could not be determined. It seemed, however, of interest to
attainpt to find out what positions the spores assumed whilst
falling. The magnification of the microscope, therefore, was
increased by using a No. 3 Leitz objective. Into the much
lessened field of view, spores in focus fell relatively less often,
and in passing across the field appeared to fall with a relatively
much greater velocity. However, the shape of the spores could
often be distinctly observed. It was found that the spores, whilst
falling the first few millimetres after leaving the gills, often turn
round and round upon themselves in an irregular manner. Longer
spores often oscillate from side to side and probably fall in very
THE RATE OF FALL OF SPORES 177
steep corkscrew-like paths. Special attention was paid to the
fall of the spores of Polyporus squamosus, which are nearly
three times as long as they are wide. It was found that on
emerging from the hymenial tubes many of them have their
long axes nearly vertical, and that whilst falling they often
appear to turn over and over on themselves or to rock from side
to side. However, by following the spores individually with the
help of a mechanical stage, it was plainly seen that after falling
about 5 mm. they were almost without exception nearly or quite
horizontal, and that they then rotated in a horizontal plane very
slowly or not at all. The final position which the spores took up
in still air was therefore such that the greatest surface was
presented to the resistance of the air. We may conclude, there-
fore, that long spores tend to fall in a similar manner to that
assumed for the simple, prismatic ice-crystals which cause the
phenomena of sun-dogs, &c., in northern regions.
APPENDIX
The compressor-cell method of measuring the rate of fall of spores was
devised in 1905. I then came to the conclusion that the spores of Hymenomy-
cetes fall at a rate which is roughly in accordance with Stokes' formula,
and this fact was announced by A. J. Ewart in his translation of PfefFer's
Physiology of Plants. 1 During the summer of 1906, I carried out a large
number of measurements of the size, specific gravity, and terminal velocity
of spores, and in 1907 Chapters XIII., XIV., and XV. were communicated to
the Royal Society as sections of a paper which I subsequently withdrew. 2
Recently Zeleny and M'Keehan 3 of the University of Minnesota have
announced that they have made a direct test of Stokes' formula by using
lycopodium power. Their method of measuring terminal velocity consisted
in allowing the powder to fall in wide tubes and noting the rate of movement
1 Vol. iii., 1906, p. 416.
2 The paper called " The Production, Liberation, and Dispersion of the Spores
of Hymenomycetes " was accepted for publication in the Philosophical Transactions
of the Royal Society, but on conditions which I was unable to accept.
3 John Zeleny and L. W. M'Keehan, "An Experimental Determination of the
Terminal Velocity of Fall of Small Spheres in Air." A paper read at the meeting
of the American Association for the Advancement of Science, held December 1908.
Abstract in Science, March 19, 1909.
M
1 78 RESEARCHES ON FUNGI
of the centre of the cloud. They came to the conclusion that for lycopodium
spores the formula gives velocities 50 per cent, in excess of those observed.
My method for testing Stokes' formula appears to have various advantages
over that used by Zeleny and M'Keehan for the following reasons. Amani-
topsis spores have smooth walls and are practically truly spherical, whereas
lycopodium spores have sculptured walls and are four-sided. Amanitopsis
spores have a diameter only about one-third as great as lycopodium spores.
In the tube method convection currents cannot be eliminated, and it must
surely be somewhat difficult to decide the exact centre of the spore clouds.
By my method of using a very small chamber, the difficulty of convection
currents was reduced so as to be negligible, and the velocities of the individual
spores could be measured with considerable accuracy. Amanitopsis spores are
liberated spontaneously by the fungus, whereas lycopodium powder requires to
be set in motion by artificial means. 1
1 The substance of this Appendix is contained in a letter to Nature on " The
Rate of Fall of Fungus Spores in Air," April 14, 1909.
CHAPTER XVI
THE EFFECT OF HUMIDITY ON THE RATE OF FALL OF SPORES
IT can be shown on mathematical grounds that, when bodies
the size of spores are allowed to fall freely in still air, they reach
their constant terminal velocity before they have gone their own
diameter or a distance of less than 10 fi. 1 It was expected
at first, therefore, that a spore would fall through the space in a
Compressor cell, i.e. a distance of about 13 mm., at a uniform
speed. Accordingly, in order to test this supposition, the rate of
fall of spores through a field of 4-55 mm. at different distances
below the gills was measured. It was soon discovered that the
velocity of a spore gradually diminished as the spore fell after
emerging from the gills. It was suspected that this was due to
the gradual diminution in size of the spore owing to loss of water
from it by drying. Comparative experiments with the air in the
chamber in different states of humidity were then undertaken.
The air of the chamber was first made as moist as possible by
means of soaked blotting-paper, next the ordinary air of the
laboratory was employed, and finally the air was dried as far as
possible with crystals of calcium chloride. A different piece of
the same fruit-body was used in each case. The results of the
observations are recorded in the Tables on p. 180. The figures give
the velocities in millimetres per second.
From these results we may conclude that, as a general rule,
the spores fall most rapidly on leaving the gills, and that the rate
of fall gradually diminishes. This appears to be so, even in
chambers which contain a free drop of water and soaked blot-
ting-paper (Fig. 58, p. 167), and in which the air must therefore
be saturated with moisture. The tiny oval spores seem to be
capable of giving off water vapour in an atmosphere saturated so
far as flat surfaces are concerned.
1 Vide infra, Chap. XVII.
'79
1 8o
RESEARCHES ON FUNGI
It is also evident that the dryer the air, the more slowly do
the spores fall. At the same distance from the gills, for Cuttybia
dryophila, the velocity of fall in a dry chamber was only about
Collybia dryophila
Field.
Touching gills
Soaked Blotting-paper in
Chamber.
Ordinary Air
of
Laboratory.
Crystals of
Calcium
Chloride iu
Chamber.
At First.
Two Hours
Later.
0-73 0-87
0-49
0-34
5 mm. lower .
0-72
0-74
0-39
0-28
10 mm. lower .
0-68
0-37
0-27
Polyporus squamosus
Field.
Soaked Blotting-
paper in
Chamber.
Ordinary Air of
Laboratory.
Crystals of
Calcium Chloride
in Chamber.
Touching gills .
1-83
1-34
0-85
3 mm. lower
1-85
1-25
0-71
6 mm. lower
1-73
1-17
0-70
7'5 mm. lower .
...
...
0-65
Field just
above crystals
Psalliota campestris
Field.
Soaked Blotting-
paper in Chamber.
Ordinary Air
of Laboratory.
Touching gills
1-48
1-27
3 mm. lower ....
U^
1-47
1-20
6 mm. lower ....
1-39
1-19
one-half of that in a moist chamber containing wet blotting-paper.
In the most dried condition the spores were falling at only one-
third the speed at which they fell in the most moist condition.
The obvious explanation of the decrease in speed of spores
THE EFFECT OF HUMIDITY
181
after leaving the gills, seems to be that the spores diminish in
size owing to the loss of water. According to Stokes' Law the
velocity varies as the square of the radius of a sphere. One must
remember that a spore has an enormous surface compared with
its mass, and therefore, when falling, can readily and quickly part
with some of its contained water. In falling 5 mm. in ordinary
air, when leaving the gills, spores of Collybia dryophila (the
smallest with which I have yet worked) were found to lose 20 P 4
per cent, of their velocity ; in falling 6 mm. the spores of
Polyporus squamosus lost 12' 7 per cent., and those of Psalliota
campestris 6 -3 per cent. The results are collected in the following
Table :
Diminution in Velocity of Falling Spores
Distance of
Species. Fall in
Millimetres.
Time in
Seconds.
Diminution of
Velocity
expressed in
Percentage of
Initial Velocity
observed.
Collybia dryophila . ; 5
11-4
20-4
Polyporus squamosus . . 6
4-8
12-7
Psalliota campestris . . I 6
4-8
6-3
Further observations were then made upon decrease in velocity
when spores were allowed to fall through a distance of 15 cm.
For this purpose a brass chamber (Fig. 62) was constructed.
The space within it was 16 cm. long, 1*1 cm. wide, and 0*6 cm.
deep. To one side of the chamber a glass plate was fixed with
cement, and to the other side a long cover-glass could be affixed
with vaseline. A piece of the fungus fruit-body, which included
parts of three or four gills, was placed in the chamber at one
end. When the latter was set in the upright position, spores
fell from top to bottom. With the horizontal microscope, obser-
vations on the velocity of the spores were made at different
distances from the gills.
The retardation in the velocity of fall was found to be most
rapid immediately after the spores had left the gills, and to
I 82
RESEARCHES ON FUNGI
continue in a more or less marked manner for about 10 cm.
A final, terminal, and fairly uniform velocity was then reached,
the time required for its attainment being less
than half a minute after the spores had been
liberated from the gills. The following curves
(Fig. 63) give the results of the observations.
Each velocity plotted is the average of about
twenty-five velocities recorded in sequence.
The curve for the Mushroom spores is re-
markable in that it first of all sinks and then
rises again. Possibly this is accounted for on
the supposition that the spores buckle up
after a certain stage of desiccation has been
reached. Such a mode of contraction would
decrease the surface exposed in falling, and
thus increase the velocity. As a matter of
fact, Mushroom spores, when drying on a glass
slide, rapidly become indented on one side so
that they more or less assume the form of a
boat.
A general conclusion which may be arrived
at from the data contained in this chapter
is, that in nature spores fall most rapidly
FIG. 02. Plan and , L . ,. , * ... . . ,
section of a long almost immediately alter liberation from the
me a aTurTng Sed t f he sterigmata whilst they are passing out from
rates of fall of the fruit-bodies between gills, down tubes, &c.,
spores at different .
distances from the and that after they have drifted in the COn-
gills. b, brass : r u r i_
g, glass , p, piece vection currents or the outer air tor about
of pileus. At s h a if a minute, they reach a steady terminal
and t are shown
two fields as seen velocity considerably less than the initial.
with the horizon-
tai microscope 6 We can only suppose that at the moment or
below 111 the "gills liberation the spores are fully turgid, and that
respectively. One- by the rapid loss of water they become dried
half actual size. J J
up in less than a minute. It is certainly a
good arrangement that the spores should fall down between the
gills or in hymenial tubes, &c., with the greatest velocity, for
they thus escape from the fruit-bodies with the least risk of
THE EFFECT OF HUMIDITY
183
very small convection currents causing them to touch the
hymenium, to which, owing to their adhesiveness, they would
become firmly attached. After liberation from the fruit-body
PotlfyVKA
3 o 78 T /O //
Distance beloio gills in centimetres.
f3 /If.
FIG. 63. Curves showing the rate of fall of spores at various distances below the
gills in a long chamber.
the spores fall much more slowly. This enables the wind to
carry them much further than would be possible if no decrease
in velocity were to take place.
NOTE. The gradual decrease in the rate of fall of spores in a chamber
saturated with water-vapour finds its readiest explanation in the supposition
that the spores gradually become smaller owing to loss of water. The assumption
that the spores lose water in a saturated atmosphere is in harmony with the
well-known fact that the vapour pressure of a drop of liquid depends on the
amount of curvature of its surface. The greater the curvature, the greater is
the vapour pressure. This is illustrated by the following experiment. If a
small piece of sulphur is placed in a tube which is then evacuated and sealed,
and if the tube is gently heated near the sulphur, the latter condenses on the
cool part of the tube in the form of a great number of very small drops of
different sizes. In the course of a day or so, one finds that the larger drops
have become still larger, and that they have a clear space round them. The
clear space gradually grows bigger. The explanation of this phenomenon is
that the smaller drops with the greater vapour pressure distil over into the
larger drops with the smaller vapour pressure. Similarly we may suppose that
the large free drop of water in the compressor cell (Fig. 58, w, p. 167) grows at
the expense of water lost by the minute falling spores owing to the great differ-
ence in the curvature of the surfaces.
CHAPTER XVII
THE PATH OF THE SPORES BETWEEN THE GILLS, ETC. THE
SPORABOLA- APPENDIX ON THE MOTION OF A SPHERE IN A
VISCOUS MEDIUM
BY methods already explained, it has been shown that it is possible
to determine by observation (1) the maximum horizontal distance
to which a spore travels when it has been shot out horizontally
from a basidium lying in the hymenium of a gill, 1 and (2) the
terminal vertical velocity with which the spore falls toward the
earth. 2 With a knowledge of these data, and assuming that the
resistance of the air is proportional to the velocity, it is possible
to calculate the initial velocity with which a spore is shot off its
sterigma, and also to map out the trajectory described.
The initial velocity with which a spore leaves its sterigma,
when projected in a horizontal direction, may be calculated as
follows :
Let V=the terminal vertical velocity,
X = the maximum horizontal distance of projection,
H the initial horizontal velocity, and
<jr = the acceleration due to gravity.
It can be shown 3 that
For spores of Amanitopsis vaginata, it has been observed that
X = 0'02 cm. and V = 0*5 cm. per second approximately, whence
H = 981xO-02
0-5
i.e. the spores are projected in the horizontal direction from the
sterigmata with an initial velocity of approximately 40 cm. per
1 Method II., Chap. XI. a Chap. XV.
3 A note on the motion of a sphere in a viscous medium is given in the
Appendix to this chapter for convenience of reference.
184
THE SPORABOLA
185
second. Since the maximum horizontal distance of projection
is 0'02 cm., it is clear that in travelling only this short distance
the horizontal velocity of a spore is reduced from 40 cm. per
second to zero. This will not seem surprising when the ratio
of the surface to the mass of the spore is taken into account.
Since the spores are shot outwards horizontally, they describe
a curved trajectory in falling toward the earth. The trajectory
is a peculiar one. In future it will be referred to as the sporabola.
It can be shown that the equation for the sporabola is
01
00*.
where V = the terminal vertical velocity,
X = the maximum horizontal distance of projection,
g = the acceleration due to gravity,
t/ = the distance of a point on the sporabola below the highest point, and
z= the distance of a point on the sporabola from the vertical axis.
Since V, X, and g are known, by assuming values for x correspond-
ing values for y
can be calculated
and the sporabola
plotted out. The
accom panying
figure represents
the sporabolas for
A manitopsis vagi-
nata and Psalliota
campestris (Fig.
64).
The sporabola
is remarkable in
that the horizontal
part passes very
sharply into the
vertical part. The
horizontal and Flo 64 _ The sporabolas of two spores shot out horizontally
Vertical motions from the hymenium. The spores, drawn to scale, are
shown below. The scale is in centimetres.
appear to be al-
most independent of one another. Direct inspection of the curve
1 86
RESEARCHES ON FUNGI
7
indicates that the horizontal velocity is reduced to zero by the
time the spore has fallen through a distance only about equal
to its diameter.
It must often happen that spores are not shot outwards in
exactly the horizontal direction but at a greater or less angle
thereto. The paths of spores projected with equal velocities
at various angles can be deduced mathematically, and are indi-
_^ cated diagrammatically in the ad-
joining figure (Fig. 65). That the
sporabola appears to consist of two
parts, one due to violent projection
of a spore and the other due to
gravitation, again becomes obvious.
We may conclude that, if a basidium
looks upwards, it will shoot its spores
to a height approximately equal to
the maximum horizontal distance to
which it would have projected them
if it had been placed horizontally
FIG 65.-Sporaboias of spores shot instead of vertically. Quite generally,
outwards from a point at various *
angles with the vertical and with the sudden bend in each sporabola
equal initial velocities. . . -11
takes place at approximately the same
distance from the point of projection at the surface of a limiting
sphere (Fig. 65).
Before attaining its steady terminal velocity, a spore requires to
fall but a very minute distance. This may be shown as follows :
Let X = the maximum horizontal distance of projection,
x = the distance of a point on the sporabola from the vertical axis,
V = the terminal vertical velocity, and
v = the vertical velocity at any time.
Then it may be deduced that
X _ V
X~V
By substituting the value of ^ in the equation for a sporabola
we get
THE SPORABOLA 187
Let us assume that the vertical velocity at any time is within
1 per cent, of the terminal velocity, and that y is the distance
the spore has fallen before attaining this velocity, then putting
log, = 2-3 Iog 10 and ^ = 0'99, we get
y= Y." | - log, (0-01) 2-3 - 0-99 |
For Amanitopsis vaginata, since V = O5 cm. per second, we find
that
y = 0-0009 cm. = 9 p.
The diameter of a spore is approximately 10 /*. Hence we can
state that the distance fallen by a spore of A. vaginata before
reaching its terminal velocity (within 1 per cent.) is less than its
diameter.
The length of time required for any spore after being set free
to attain its terminal vertical velocity within 1 per cent., can be
shown to be equal to 0'0047 x V, where V is the terminal velocity.
For Amanitopsis vaginata the terminal velocity may be taken as 0-5
cm. per second. It can be calculated, therefore, that a spore would
attain its terminal vertical velocity in approximately ^^ second.
The terminal velocities of fall of the spores of other species are of
the same order as that of Amanitopsis vaginata. We are therefore
justified in drawing the general conclusion that the spores of
Hymenomycetes attain a uniform velocity of fall practically at the
instant of their liberation.
We can also calculate the length of time required for a spore to
arrive within 1 per cent, of the total horizontal distance to which
it is projected. At the end of the time in question, the position of
the spore on the sporabola will be x cms. from the vertical axis
and y cms. below the highest point. According to our assump-
tion x = 0-99. By substitution in the equation for a sporabola we
.X.
find that
y = 0-0009 cm. = 9 p.
It has been shown, however, that a spore falls through this
distance in approximately -^ second. We may conclude, therefore,
that the spore will have travelled for only T ^ 7 second before arriving
1 88 RESEARCHES ON FUNGI
within 1 per cent, of the total horizontal distance to which it is
projected. An important conclusion which may be drawn from this
calculation is that it would be extremely difficult, if not impossible,
to observe the horizontal flight of the spores. The horizontal move-
ment is completed in ^^ second. It is very questionable if the
human eye could observe such a movement of a dark body at all,
and particularly under the conditions of observation necessitated by
the size of the spores, the position of the basidia, and the uncertainty
of the time of spore-discharge. These theoretical considerations fall
in line with my observations, for I have never yet succeeded in
watching the horizontal flight of a spore from its sterigma.
The results of the investigations upon the motion of a spore of
AmaniiopeiB vaginata, 10 /* in diameter, when projected from its
sterigma in a horizontal direction, may be summed up as follows :
By observation
Maximum horizontal distance of projection = 0'02 cm.
Terminal velocity of fall = 0'5 cm. per second.
By calculation
The terminal velocity of fall is reached after a distance of 9 n (which is
less than the diameter of a spore) has been traversed.
The terminal velocity of fall is reached in ^^ second approximately.
The spore arrives within 1 per cent, of its total horizontal flight (i.e. it
goes 0*0198 cm.) in j^y second.
The initial horizontal velocity is 40 cm. per second.
When one compares the movement of a spore with that of a
pebble projected in like manner, the differences at first appear to be
remarkable. However, it must be remembered that a spore has an
enormous surface in proportion to its mass as compared with a
pebble. The air, therefore, in proportion to their masses, offers a
vastly greater resistance to the movement of a spore than to that of
a pebble.
In Plate I., Fig. 4, the paths of spores between the gills of a
Mushroom are shown, whilst in the text-figures 56 (p. 165) and 66
similar illustrations are given for Amanitopsis vaginata and Poly-
porus squamosus respectively. It is evident that the spores are
shot outwards from the hymenium in such a manner that they are
projected clear of the hymenium and yet not far enough to strike
the opposite gill. The air is a delicate regulator in this matter.
THE SPORABOLA
189
The structure of a Mushroom is such that the spores are shot out
into the spaces between the gills, where they fall down freely in
response to gravity. They thus escape from the fruit-body without
danger of touching, and thereby adhering to, the hyinenium.
The hymenium on the side of a gill may be likened to a battery.
The basidia are the guns and the spores the projectiles. Each gun
is capable of shooting off four projectiles
in succession at intervals of a few seconds
or minutes. The battery is so splendidly
organised that the guns are brought for-
ward, mounted, and fired off in succes-
sion. Thus a heavy and continuous
boinbardment is maintained for days or
weeks, and only ceases when the am-
munition has become exhausted. The
object of the miniature gunnery is to
drop the spores into the spaces between
the gills, so that they may fall out from
the fruit-body without touching one
another or any part of the hymenium.
The success with which a large Mush-
room or Polyporus is able in the course
of a few days to liberate thousands of
millions of spores, and entrust them to
the scattering winds, may well excite our
admiration.
In a few rare instances, owing to
imperfection in the structure of the pilei, the spores are not all
able to escape into the outer air. Thus, for example, in Nolanea
pascua the gills often become locally powdered with the red spores.
This is due to the fact that the gills are somewhat wavy, and there-
fore not properly disposed in vertical planes. The adhesive spores,
when falling, catch and stick on the projecting parts.
FIG. 66. Vertical section
through two hymenial tubes
from the pileus of Polyporus
squamosus. The arrows show
the sporabolas described by
the spores when they are
discharged, h, the hyme-
nium. About 8 times natural
size.
190 RESEARCHES ON FUNGI
APPENDIX
THE MOTION OF A SPHERE IN A VISCOUS MEDIUM
Contributed by Dr. GUY BARLOW.
(The notation is the same as that employed in Chapters XV. and XVII.)
As shown by Stokes, the resisting force on a sphere of radius a when moving
with velocity v is given by
Since the force is directly proportional to the velocity, it is evident that the
component of this force in any direction is also directly proportional to the
component of the velocity in that direction. The motion of the sphere when
projected under gravity can therefore be regarded as compounded of the
independent horizontal and vertical motions, and these may be conveniently
investigated separately.
1. Fall from rest under gravity.
The equation of motion is
dv
m j- = mg btrfj.av,
where m is the mass of the sphere and v its velocity downwards at time t.
The density cr of the medium is here neglected.
This equation may be written
dv
5 =*- ... (2)
where
When the steady terminal state is reached, _? -= 0, v = V, hence from (2),
V=f . (3)
Substituting value of c and putting m = ~Tra 3 p we obtain Stokes' expression
O
for the terminal velocity
T-|^?. . (4,
Equation (2) may now be written
5**?*
Integration with initial condition v o when t = o gives
v = V (l-e- c ') (5)
THE MOTION OF A SPHERE 191
Putting v = -j- and integrating again with condition y = o when t = o we get
y = V\t- l -(l-e-)\ -.. . . . . (6)
2. Horizontal motion with initial velocity H.
If u is horizontal velocity at time t, the equation of motion is now simply
du
dt=- cu '
or
du
U -y- = - CM.
ax
Therefore
d = - cote,
and hence
H-M = CX . (7)
But a; = X for u = o, therefore H = cX.
From the last expression and (3) we obtain
H=f (8)
Proceeding with the integration, from (7) we have
dx
~dt =u
= H-cx
= e(X-z).
Integration with initial condition x = o when t = o leads to
*=X(l-e-<*) (9)
3. The equation of the path of a sphere projected horizontally under gravity
is obtained at once by the elimination of t from the two equations (6) and (9) ;
and replacing c by its value ^ we have finally
"7 1 X'-xH! (i)
CHAPTER XVIII
THE ELECTRIC CHARGES ON THE SPORES
ALTHOUGH the matter may be of but small biological interest, it
seemed desirable to ascertain whether or not the falling spores
carry electric charges, and, if so, of what kind. The apparatus for
the investigation of the problem was constructed as follows. A
brass chamber, shown at B by two sections in Fig. 67, was supported
on a rod, R, and covered in front and behind with glass discs, GG'.
At its centre were fixed two brass plates, PP', 1/2 cm. wide and
2 cm. high, so that they were parallel to one another and about
1*5 mm. apart. The plates were attached to wires introduced
through lateral holes in the chamber, insulation being secured by
means of glass tubing, TT', and sealing-wax, S. Above the plate
was suspended a piece of the pileus of a Mushroom, F, with the
gills looking downwards. This was held in position by means
of a pin stuck into a cork, K, covered with tinfoil, N. The brass
chamber, and thus also the piece of fungus, was carefully earthed
by means of a wire attached to a gas-pipe at E. By means of
other wires the two plates were connected with a mercury com-
mutator, C. The latter was then connected on one side with the
gas-pipe, E, and on the other with the city main, M, of 220 volts.
The lamp, L, was placed in the circuit for the purpose of detecting
any accidental flow of current. By moving the handle of the
commutator to the right, both the piece of fungus and the brass
plates were earthed and therefore rendered neutral, whilst by
moving it to the left the plates were given charges of opposite
signs.
A vertical plane, passing between the plates towards their
centres, was focussed and observed by means of a horizontal
microscope with a magnification of about 25 and a field of
view 5'5 mm. in diameter (cf. Plate IV., Fig. 29). When the
192
THE ELECTRIC CHARGES ON THE SPORES 193
handle of the commutator was turned to the right so that the
plates were uncharged, the spores could be seen falling vertically
downwards between them at the rate of about 1 mm. per second.
No attraction of the spores to the plates could be detected. When
spores were observed to have reached the centre of the space between
the plates, the handle of the commutator was suddenly turned
to the left so that one of the plates became positively and the
other negatively charged. Immediately the paths of most of the
spores were altered (Fig. 68, A). Some spores were attracted to
one plate and some to the other, the majority going to the one
FIG. 67. Apparatus with electrical attachments for detecting the electrical
charges on falling spores. The brass chamber B, natural size. Description
in the text.
with a positive charge. A few continued their motion vertically
downwards. A number of spores appeared to turn at right angles
to their former courses and they then moved with great rapidity
to the plates. These must have been the spores which were
relatively the most highly charged. Others made their way to
the plates at a more or less gentle angle to the vertical and with
a less accelerated velocity. Doubtless they were less highly
charged. A certain number of spores which were not appreciably
affected by charging the plates were probably not electrified at all.
On reaching one of the plates, each spore became charged with
electricity of the same sign as that on the plate, and in consequence
194
RESEARCHES ON FUNGI
tended to be repelled from the latter. Owing to their adhesiveness,
however, the spores were unable to leave the plates after having
once come in contact with them. When the plates were left
charged for some hours, the spores, which fell in large numbers
from the piece of pileus, gradually formed simple or branching
chains which sometimes stretched almost from one plate to the
other, thus indicating the direction of the lines of force between
them. The formation of chains not only demonstrated the
FIG. 68. The paths of spores falling between two brass plates. A, shows how
the spores deviate from the vertical when the plates are suddenly electrified
with charges of opposite signs. B, zigzag path of a spore produced by
alternately reversing the charges on the plates. C, path of a spore pro-
duced by charging the plates, making them neutral, giving them reversed
charges, &c., in succession.
tendency of the spores to be repelled from the plates and from
one another, but also the fact that the spores strongly adhere
to surfaces with which they may come in contact.
When the plates were suddenly charged, it was found that
proximity of a spore to one plate rather than the other was not
a factor deciding to which of the two plates the spore should
move (Fig. 68, A). There seems to be no escape from the conclusion
that, either at the moment of discharge from the sterigmata or
within a very few seconds afterwards whilst falling through the
air, the majority of spores receive positive or negative electric
THE ELECTRIC CHARGES ON THE SPORES 195
charges of different strengths, whilst a certain number do not
become charged at all.
By another arrangement of the commutator, it was possible to
reverse alternately the charges on the plates or to remove them.
By reversing the charges alternately a spore can be made to take
a zigzag path across the field like that shown in Fig. 68, B. By
successively charging the plates H , 00, K 00, H , &c., one
can make the path of a spore still more irregular (Fig. 68, C).
Several other species beside Psalliota campestris were tested,
among them being Polyporus squamosus. In all cases the spores
behaved like those of the Mushroom, the majority appearing to
be charged, either positively or negatively.
That the spores bear electric charges during their passage through
the air may be regarded as a physical fact of no apparent biological
importance. There seems to be no reason to suppose that in
nature the spores, in consequence of being electrified, settle on
one surface rather than another. It therefore appears improbable
that the charges are of use to the spores in enabling them to obtain
advantageous locations for germination.
A further investigation as to the manner in which the spores
originally become charged and into the conditions which determine
the gain or loss of charges by them was thought unnecessary for
my present purpose.
CHAPTER XIX
THE COPRINUS TYPE OF FRUIT-BODY
" And agarics and fungi with mildew and mould
Started like mist from the wet ground cold ;
Pale, fleshy, as if the decaying dead
With a spirit of growth had been animated !
Their moss rotted off them, flake by flake,
Till the thick stalk stuck like a murderer's stake,
Where rags of loose flesh yet tremble on high,
Infecting the winds that wander by."
SHELLEY. 1
THE Coprini are especially characterised by the fact that the gills
" deliquesce " on maturity, and that drops of an inky -looking fluid
are often formed on the pilei. So far as I am aware, however,
although many figures and photographs 2 of members of the
Coprinus genus have been published, no one hitherto has ex-
plained the real significance of the fact of " deliquescence " or the
general structural arrangement of Coprinus fruit-bodies. In what
follows, I hope to be able to show how admirably a Coprinus
fruit-body is constructed when regarded as a highly efficient
spore-producing and spore-liberating organ.
One of the best known and largest of the Coprini is Coprinus
comatus. It often comes up in great abundance in fields
(Plate IV., Fig. 21). It "deliquesces" in a typical manner.
Fruit-bodies of this species afforded me admirable material for a
study of the structure of a Coprinus in relation to spore-fall.
1 The second of these two verses evidently refers to a species of Coprinus.
The poet had probably noticed the remarkable changes which take place in the
conspicuous fruit-bodies of Coprinus comatus.
2 A series of excellent photographs of this species has been published by
G. F. Atkinson, " Studies and Illustrations of Mushrooms : II.," Bull. 168, Cornell
Univers. Agric. Experiment Station, 1899; also, Mushrooms Edible, Poisonous, dr.,
Ithaca, 1901, pp. 33-41.
196
THE COPRINUS TYPE OF FRUIT-BODY 197
An unripe pileus which has attained its full length is more or
less barrel-shaped (Plate II., Fig. 7 ; Plate IV., Figs. 21 and 22, to
the right). The gills are white in colour, closely packed together,
and with very few exceptions equal in length.
Upon beginning to open out, the pileus alters its form from
that of a barrel to that of a bell (Plate IV., Figs. 21 and 22;
Plate I., Fig. 1). It breaks away from the stipe below and leaves
the latter encircled with an annulus. Whilst the gills are moving
radially outwards from the stipe, they become slightly separated
from one another. The rim of the bell-shaped pileus now turns
slightly outwards (Plate I., Fig. 1). This results in a further
separation of the . lower ends of the gills, so that the spaces which
have thus arisen between them are similar to those between the
gills throughout their' whole length in the case of a Mushroom
(cf. Plate IV., Figs. 23 and 25). Except at their lower ends,
adjacent gills at this stage in development are united by inter-
locking cystidia along their margin, and are just as closely packed
as they were when the fruit-body was barrel-shaped. The separa-
tion of the lower ends of the gills is accompanied by the beginning
of the process of " deliquescence."
Whilst the pileus is changing from the barrel to the bell form
and is separating the lower ends of its gills, the basidia are rapidly
developing their spores. As these ripen they turn pinkish and
finally black. Just before "deliquescence" begins, it can clearly
be made out that the spores ripen on the gills from below up-
wards. The lower parts of the gills blacken first (Plate I., Fig. 1).
The black zone passes into a pink zone higher up, and this in its
turn, toward the top of the pileus, gradually shades into white.
Whenever a gill has become black, a small piece of its surface,
when seen in face view with the microscope, has the appearance
shown in Plate III., Fig. 15. The pattern presented to the eye
is very regular and pleasing. Each basidium bears four black
spores, and is separated from adjacent basidia by paraphyses.
The four spores of a basidium are so attached to the sterigmata
that they are separated from one another as much as possible.
They are thus prevented from touching, and consequently from
adhering to, one another both during development and discharge.
198
RESEARCHES ON FUNGI
The paraphyses are present in just the right proportion to prevent
the spores of adjacent basidia from coming in contact. A glance
at Plate III., Fig. 15, shows that the spacing of the adhesive
spores is brought about so economically that it would be difficult
to imagine how more of them could be developed simultaneously
on any given area of a gill surface. A cross-section through a
gill (Plate III., Fig. 16) shows that the basidia project considerably
beyond the paraphyses and are all directed perpendicularly out-
wards from the gill surface.
When the pileus is still barrel-shaped and until spore-fall
FIG. 69. Coprinus romatus. Fruit-bodies in an early stage of development.
In the tallest the fall of spores and autodigestion have just begun. The
four others are a few hours younger : the pilei are separating from the
stipe below and the gills are still intact. Photographed at Sutton Park,
Warwickshire, by J. E. Titley. About natural size.
begins, the inner edges of the gills towards the stipe, throughout
their entire length and for a width of about O25 mm., appear to
the naked eye as white bands (Plate I., Fig. 1, m; Plate II.,
Figs. 8 and 9, ra). These are especially inflated portions of the
gills, entirely devoid of basidia and covered over by large, colour-
less, unicellular cystidia (Plate III., Figs. 13 and 14). The
THE COPRINUS TYPE OF FRUIT-BODY
199
thickened marginal bands of adjacent gills are in contact with
one another, so that a solid white cylinder is formed which en-
sheaths the stipe. It is important to notice that the gills,
except where they join at the membranous flesh of the pileus
and are in contact by means of the inner inflated marginal bands,
FIG. 70. Voprinus comatua. Same fruit-bodies as shown in Fig. (>9, twenty-two
hours older. All are shedding spores and undergoing autodigestion. The
pileus of the tallest has become reduced to one-half its original size and a
few drops of inky fluid have fallen from its recurved rim on to the pilei
below. The stipes have lengthened considerably. Photographed at Button
Park, Warwickshire, by J. E. Titley. About ^ natural size.
are separated throughout their entire length (Plate I., Fig. 5).
In the spaces thus provided between the gills, the projecting
basidia can freely develop to maturity (Plate III., Fig. 14). It
thus happens that the spores of basidia, which belong to adjacent
gills, are never in danger of coming into actual contact and con-
200 RESEARCHES ON FUNGI
sequently of adhering to one another. The significance of the
marginal bands with their cystidia seems to be, therefore, that
they secure that the faces of adjacent gills, i.e. the hy menial
surfaces, shall be suitably spaced during development. 1
The so-called " deliquescence " of a Coprinus fruit-body has
nothing in common with the phenomenon of deliquescence of
crystals known to the chemist. The phenomenon with which we
have to deal is really a process of autodigestion. The solid parts
of the gills become fluid, in all probability through the agency
of digestive enzymes. There is not the slightest reason to suppose
that the fluid is derived from the water-vapour of the air.
Autodigestion of a gill always begins at its base, along the
free edge where the gill is separating or has just separated from
its neighbours (Plate II., Fig. 8, s). The marginal cystidia are
first involved. They simply break down, become fluid and indis-
tinguishable. After the destruction of the cystidia, the auto-
digestion proceeds obliquely upwards and gradually destroys the
whole gill (Plate II., Figs. 8, 9, 10, and 11). The entire destruction
of the gills from below upwards in large fruit-bodies was observed
to take about two days, whilst in smaller ones the process was
carried out in little more than twenty-four hours (cf. Figs. 69,
70, and 71).
As the gills get shorter and shorter owing to their destruction
from below upwards, the pileus gradually opens. It passes from the
bell shape to the helmet shape (Plate II., Fig. 9), and at length,
as it becomes smaller and smaller, flattens out into a disc like
that of a Mushroom (Plate II, Fig. 10 ; Plate IV., Figs. 21 and 22).
The remains of the gills thus come to be held out horizontally.
In this position they disappear in their entirety, so that merely
the naked central flesh of the pileus is left behind (Plate II, Fig. 11).
When a fruit-body has completely lost its gills, the stipe often
bends in two toward the middle, so that the pileus flesh, which has
now become very discoloured and ragged, either hangs down or
1 It might perhaps be shown that the provision of spaces, so that the basidia
can develop their spores in air without contact with any obstacle, is a principle of
development applying not only to the Coprini, Psalliota, Polyporus, &c., but to
the Basidiomycetes generally.
THE COPRINUS TYPE OF FRUIT-BODY
201
comes in contact with the ground. The further destruction of the
fruit-body appears to be completed by putrefaction. From the
first appearance of a very young fruit-body above the ground up
to the giving way of the stipe, the interval was found to be about
seven days.
It sometimes happens that, shortly after autodigestion has
FIG. 71. Coprinus comatus. Last stages in autodigestion. The fruit-body to the left
has lost about three-fourths of its pileus but is still shedding spores. The same
fruit-body, twenty-four hours older, is shown on the right. The gills have now
practically disappeared and spore-emission has ceased. Photographed by P. Grafton.
^ natural size.
begun, the free margin of the pileus presents a rayed or ragged
appearance. This is due to the fact that, at intervals round the
base of the pileus, the lower ends of individual gills have split
along their median planes from without inwards, and that the
two halves of each gill so divided have been pulled apart laterally
(Plate IV., Fig. 23). The fissures seen at the bottom of the pileus
202 RESEARCHES OX FUNGI
from without correspond, therefore, not to spaces between adjacent
gills, but to spaces between half gills pulled asunder.
During autodigestion, the oblique free edge of each gill is black
and covered with a liquid film. From this edge evaporation takes
place and no actual drops of inky fluid form upon it. The spaces
between the gills, therefore, do not become choked up, but remain
open just as in a Mushroom (Plate IV., Fig. 23). As autodigestion
proceeds, each gill, when seen in face view, gets narrower and
narrower below, until it is almost reduced to nothing (Plate II..
Fig. 8). The membranous flesh of the pileus bearing the remains
of the gills often curls outwards and upwards so as to form a neat
and curious circular roll (Plate IV., Figs. 22 and 24; Plate III,
Figs. 9 and 10). Sometimes, however, it simply hangs downwards,
in which case the pileus looks ragged and untidy (Plate II., Fig. 8;
Plate IV., Fig. 21). With the continuance of autodigestion, the
now useless material just described is gradually converted more or
less completely into drops of inky-looking fluid, which may often
be seen hanging from the rim of the pileus (Plate II., Fig. 10 ;
Plate IV., Fig. 24). It will shortly become clear that the formation
of the circular roll on the top of the pileus is to be regarded as
an admirable method of securing that that part of the pileus which
has ceased to have any functional significance shall be as far
removed as possible from the paths of the falling spores, and thus
prevented from hindering spore-disposal by the wind.
If one allows an upright fruit-body, with its stipe placed in wet
sand, to shed its spores under a bell-jar, one finds by microscopic
examination that the inky drops, produced by autodigestion, consist
of a brown fluid containing granules but practically free from spores.
The fluid, therefore, is not made black by spores. The colour is
probably due to an oxydase which unites the oxygen of the air
with some substance liberated from the dying cells, for it was
found that the colourless juice squeezed from an unripe pileus
turns brown in a few hours. 1 The drops collect only on the rim of
the pileus, where they do not interfere with the liberation of the
spores into the air. If paper is placed round the base of the stipe,
1 Cf. A. H. R. Buller, " The Enzymes of Polyporus squamosus," Ann. of Bot. y
vol. xx. p. 51.
THE COPRINUS TYPE OF FRUIT-BODY 203
a black spore-deposit collects upon it, which is similar to that
produced under the same conditions by an ordinary Agaric.
In nature, the fluid produced by autodigestion is largely got
rid of by evaporation. The amount of it adhering to the pileus
rim varies considerably according to the state of the weather. In
very dry weather, it often happens that actual drops are not formed
at all. On the other hand, dripping is favoured by a saturated
atmosphere, and was found to take place regularly with fruit-bodies
placed in a damp-chamber.
Two independent observers have informed me that they have
been surprised by finding that the drops hanging from the pileus
of certain fruit-bodies were red instead of black. In one case the
colour was described as "just like that of red currants." I, myself,
have never seen any 'red drops, but can scarcely doubt their
occasional occurrence. Possibly the red drops were merely ex-
creted from the exterior of the pileus like those given out by
Fistulina hepatica or Lentinus lepideus, and they may have had
no connection with the process of autodigestion.
A fruit-body begins to liberate its spores as soon as it has become
bell-shaped and the lower ends of the gills have separated. The
spores are projected violently from their sterigmata into the spaces
between the gills, where they describe sporabolas, and thus escape
into the outer air. Proofs that the four spores of a basidium are
shot off in succession in the course of a few seconds or minutes have
already been given. 1 The nature of a sporabola has likewise been
dealt with. 2 Convincing proof that the spores are liberated into the
air may be obtained, not only by collecting the thick black spore-
deposit on white paper, but also by the beam-of-light method.
When a fruit-body is placed upright in a closed beaker, the beam
of light reveals clouds of spores emerging from the gills and
becoming scattered by convection currents in the enclosed air. 3
Spore-discharge from a gill is not general all over its surface
as in a Mushroom, but extremely local. It begins on both sides
simultaneously, towards the base along two opposite and very
narrow zones (Plate II., Fig. 8, s), which run parallel to and adjoin
the oblique, free, inner gill edge. We may refer to a part of
1 Chap. XT., Method IV. 2 Chap. XVII. Cf. Chap. VII.
204 RESEARCHES ON FUNGI
the hymenium where spore-discharge is actively taking place as
the zone of spore-discharge. Such a zone may be two or more
centimetres long, but it is only a fraction of a millimetre wide.
A zone of a gill, where spore-discharge is taking place rapidly,
becomes entirely spore-free owing to the fact that all the basidia
within it discharge their spores almost simultaneously. The two
opposite zones of spore-discharge on a gill gradually move upwards
together and parallel to themselves. Thus, in the course of about
two days, all the spores on a gill are successively discharged from
below upwards.
With the commencement of spore-discharge, or possibly just
previously thereto, the marginal cystidia bordering the zone of spore-
discharge break down, and become fluid and unrecognisable. The
discharge of spores leads to the production of a zone of spore-free
gill surface. Before this has become 0'5 mm. wide, it becomes
subjected to the process of autodigestion. The basidia at the gill
edge, which were the first to discharge their spores, together with
the paraphyses between them, rapidly lose their sharp contours,
become entirely disorganised, and turn into fluid. The subhymenial
cells and those of the traina break down in a similar manner.
Thus the gill edge, for a distance of about two centimetres, becomes
converted into a dark liquid film (Plate II., Fig. 8, a). We can
now distinguish five zones on each surface of a gill, running parallel
to its oblique edge (Plate II., Fig. 12). Highest of all is a zone with
basidia bearing ripe spores. Below this is the narrow zone of spore-
discharge, where the basidia are all rapidly freeing themselves of
their spores, by shooting them out one by one into the interlamellar
spaces. Further below, there is a narrow zone of spore-freed surface
where the basidia all have naked sterigmata. Below this again
is the zone of autodigestion where the basidia and paraphyses
are becoming disorganised and liquefied. Finally, occupying the
extreme gill edge, there is a dark-coloured, adhesive, liquid film.
By watching a piece of a gill like that represented in Plate II.,
Fig. 12, when placed in a closed compressor cell, it is easy to
determine that the zone of autodigestion follows hard upon the
zone of spore-freed surface. However, it never invades the zone
of spore-discharge, although it is always less than a single milli-
THE COPRINUS TYPE OF FRUIT-BODY 205
metre behind it. The five zones described, retain the same
relations to one another during the whole two days or so required
for the complete discharge of the spores. They move upwards
simultaneously from the bottom to the top of each gill (Plate II.,
Figs. 8, 9, and 10). The zone of spore-free basidia, and the adjacent
portions of the zones of spore-discharge and autodigestion, can
often just be distinguished with the naked eye upon a gill, for
together they give the appearance of a very thin whitish line
next to the thin black liquid film on the gill edge and separating
this from the general gill surface which, owing to the vast number
of spores borne by the mature basidia, is uniformly black.
It is evident that autodigestion plays a very important part
in spore-discharge. Its function is wholly mechanical. It destroys
the spore-freed portions of the gills and so clears them out of the
way. Only by the removal of these obstacles could the pileus
gradually turn outwards and thus cause the production of spaces
between the lower ends of the gills higher and higher up as these
become shorter and shorter. Such spaces are absolutely necessary
to permit of the liberation of the spores from the zones of spore-
discharge. The basidia shoot out their spores horizontally into
the spaces between the gills (Plate III., Figs. 16 and 17). The
maximum horizontal distance to which the spores travel, before
their horizontal motion is reduced to zero by the resistance of
the air, is about 0*1 mm. After making the usual sporabolic
curves, the spores fall vertically downwards with a steady terminal
velocity of about 4 mm. per second. 1 Since the zones of spore-
discharge are so near the gill edges, the spores have only to fall
a distance of about - 5 mm. between two gills in order to effect
their escape. The risk of the spores striking the gill sides is
thereby reduced to a minimum. As the spores fall below the
pileus, doubtless they lose water rapidly. 2 Their velocity pro-
bably diminishes to about 2 mm. per second in the course of a
minute. On leaving the fruit-body, the spores are carried off
by air-currents which scatter them far and wide. The discharge
of spores into the air takes place day and night continuously. It
has already been mentioned that a large fruit-body was found to
1 Chap. XV. * Chap. XVI.
206
RESEARCHES ON FUNGI
produce about 5,000,000,000 spores. 1 Since the entire discharge
of the spores from a large pileus usually takes about 48 hours,
it seems safe to state that in this case more than 1,000,000 would
have been liberated upon the average each minute. One need
not therefore be surprised at the rapidity with which a black
spore - deposit collects
upon white paper, Avhen
this is placed beneath a
fruit-body which has its
natural orientation under
a bell-jar (Fig. 72).
My OA\ r n observations
seem to point conclu-
sively to the fact that
the spores of Coprinus
comatus, like those of
the Mushroom and all
other Agaricinese, are dis-
tributed by the wind.
HoAvever, another, and I
believe quite erroneous,
explanation of this mat-
ter, has found its Avay
into botanical literature.
FIG. 72. The liberation of spores by Coprinus comatus. I fc SCCIUS to have been
The fruit-body was gathered in a field and then eiio-o-pstpd oricrinflllv bv
set in a vertical position under a bell-jar. As the su g esl originally Dy
pileus expanded below, spores began to fall. The Fulton, 2 and IS now given
black spore-deposit upon the paper around the . .
base of the stipe was formed in the course of in Various text-books. It
natural s"e S .' Photographed by P " Grafton " * has been stated that the
gills turn into an inky
mass, that the fluid so produced contains the spores, and that
insects visit the fruit-bodies, lick up the ink, carry off the spores,
and thus spread them from place to place. This seems to me
^ Chap. V.
2 T. W. Fulton, "The Dispersal of the Spores of Fungi by the Agency of
Insects, with special reference to the Phalloidei," Ann. of Bot., vol. iil, 1889-90,
pp. 215-216. I fail to follow Fulton in finding a resemblance between the pilei
of Coprini and the capitula of Compositse.
3 E.g. E. M. Freeman, Minnesota Plant Diseases, 1905, pp. 178-179.
THE COPRINUS TYPE OF FRUIT-BODY 207
to be nothing more than an assumption based on an imperfect
analogy with the phenomena of spore - dispersion in Phallus
impudicus and other Phallinese. I have carefully watched auto-
digesting fruit-bodies of Coprinus comatus in the field and have
failed to observe any insects visiting them. The absence of any
red or suggestive colour on the exterior of the pileus and the
scarcely noticeable and inoffensive odour, are additional facts
pointing to the conclusion that the fungus has no special arrange-
ments with insect visitors. The chief evidence in refuting the
insect theory, however, is that the liquid drops which in moist
weather hang from the margin of the pileus, contain practically
no spores. The few which are present, doubtless, have got into
them by accident. It seems quite certain that the majority of
the spores are always carried off by the wind.
Upon gathering "deliquescing" fruit-bodies of Coprinus comatus,
mycologists usually find it convenient to lay them more or less
horizontally in the collecting tins in order to bring them to the
laboratory. Under these conditions, in the course of an hour or
so, the lower ends of the gills, where autodigestion is taking
place, become hopelessly stuck together and the spaces between
their ends blocked up. The dark fiuid then becomes laden with
spores. The delicate mechanism for securing the liberation of
spores into the air thus becomes entirely spoiled. Possibly, the
sight of the gills stuck together in an inky mass in this way has
given rise to the erroneous impression that the spores in nature
become involved in the putrescent fruit-body. In order to study
the phenomenon of spore-liberation in its normal course, the best
plan is as follows. One gathers a large fruit-body which is opening
out below and has therefore reached a stage in its development
just previous to the beginning of autodigestion. One lays the
fruit-body in a vasculum in any convenient position and, on
arrival at the laboratory, one plants it upright in wet sand by
means of its stipe, so that it comes to have the same orientation
that it had when growing in nature. In the course of a few hours
normal autodigestion begins at the bottom of each gill and pro-
gresses upwards just as in the field. The spaces between the ends
of the gills remain open, and, if the fruit-body is covered with a
208
RESEARCHES ON FUNGI
bell-jar, the spores discharged into the air can be collected on
paper.
Spore - deposits can be collected on paper from any of the
Coprini. I have obtained spores in this way not only from
Coprinus comatus
but also from C.
atramentarius, C.
micaceus, C. fime-
tarius, var. cinereus,
as well as from a
number of smaller
species. Duggar l
is therefore in error
when, in discussing
the means of mak-
ing pure cultures
of edible Hymeno-
mycetes, he says
" members of the
genus Coprinus are
deliquescent, and
here it is imprac-
ticable to procure
spores by the spore-
print method."
With the exercise
of a little care, one
can obtain as dense
a spore-deposit from
a Coprinus coma-
tus as from a Mush-
FlG. 73. Fruit-bodies of Coprinus atramentarius shedding
spores. Although the lower parts of the stipes are
oblique, the upper parts are vertical, so that the gills
lie in vertical planes. The lower parts of the pilei are
splitting so as to permit of the requisite separation of
the gills which are undergoing autodigestion. Photo-
graphed at Sutton Park, Warwickshire, by J. E. Titley.
Reduced to about f
Coprinus atramentarius (Fig. 73) and C. micaceus (Fig. 74)
were found to shed their spores in essentially the same manner
as C. comatus. C. plicatilis, and other very small species, behave
1 B. M. Duggar, " The Principles of Mushroom Growing and Mushroom Spawn
Making," U.S. Dep. of Agric., Bureau of Plant Industry, Bulletin No. 85, 1905, p. 22.
THE COPRINUS TYPE OF FRUIT-BODY 209
somewhat differently. The gills ripen and shed their spores from
below upwards. As the pileus opens out, the necessary inter-
lamellar spaces widen from below upwards. However, the entire
opening of the pileus, which eventually becomes disc-shaped, is
accomplished without "deliquescence." Each gill splits vertically
from above and the two halves become pulled out laterally. The
expansion of the pileus and the necessary spacing of the gills is
thus satisfactorily brought about without autodigestion, which
process in these tiny fruit-bodies would be superfluous.
Massee 1 has recently stated that " Many species included in
Coprinus as C. plieatUis and others having dry, non-deli-
quescent gills, have no real affinity with this genus." Now
that the function of autodigestion has been discovered, this view
can no longer be regarded as tenable. Autodigestion alone is not
a decisive test for placing a species in the genus Coprinus.
In its absence in the smaller species, such as C. plicatilis,
Coprinus characters, e.g. thinness of the flesh, general structure
and splitting of the gills, protuberant basidia separated by para-
physes of a special type, and particularly the ripening and dis-
charge of the spores in succession in a direction proceeding from
the pileus margin to the pileus centre, are still sufficiently obvious.
Even in C. plicatiloides (Fig. 26, p. 70), one of the smallest of all
Coprini, where the expanded parasol-like pileus is often only 5 mm.
or even less in diameter, the process of spore-discharge proceeds
centripetally. It always begins first, and is completed first,
around the periphery of the pileus, and the last spores to be set
free are those in the neighbourhood of the stipe. The gradual
progress of spore-discharge is therefore essentially similar in
the diminutive C. plicatiloides and in the relatively gigantic
C. comatus. This seems to me to be strong evidence that both
species have been rightly placed within the same genus.
There can be little doubt that some of the smaller and more
delicate species of Coprinus are largely dependent on the weather
for success in liberating their spores into the air. In very dry
weather, especially when it is windy, I have noticed that fruit-
bodies of C. plicatilis, growing on a lawn, and those of
1 G. Massee, Text-Book of Fungi, London, 1906, p. 364.
O
2IO
RESEARCHES ON FUNGI
Coprinus micaceus, shrivel up before spore-discharge has been
completed, and sometimes, indeed, without its beginning at all.
Doubtless this is due to too rapid transpiration from the gills
and upper surface of the pileus. In moist weather the gills of
C. micaceus undergo the typical process of autodigestion, which
has the same relation to the zones of spore-discharge as in
C. comatus. Stages in the opening out of the pileus and in
FlG. 74. Coprinus micaceus. A group of fruit-bodies in a late stage of
development. The gills have almost disappeared owing to autodigestion.
The rim of the pileus in the foreground is markedly recurved. Photo-
graphed at Sutton Park, Warwickshire, by J. E. Titley. About
natural size.
the disappearance of the gills of C. micaceus are shown in
Plate III., Figs. 18, 19, and 20.
As a result of my investigations, I have come to recognise two
distinct types of spore-producing and spore-liberating fruit-bodies
in the Agaricineae. One is represented by the Mushroom and
the other by C. comatus. The former is by far the more
common and includes all ordinary Agaricinese, whilst the latter
is restricted to the "deliquescing" Coprini. The significant
THE COPRINUS TYPE OF FRUIT-BODY
211
points of difference between the two types may be tabulated as
follows :
Xo.
1'salliota campestris.
Coprinus comstiis.
1
Flesh thick.
Flesh very thin or mem-
branous.
2
Gills more or less hori-
zontally outstretched at
maturity.
Gills more or less vertically
placed at maturity.
3
Spores not at all ripe or
all discharged simultane-
ously on any part of a
gill.
Spores all ripen and are
all discharged simultane-
ously in a narrow zone
which progresses slowly
from the base to the top
of each gill.
4
Gills do not undergo a pro-
cess of autodigestion.
Gills become destroyed by
autodigestion from below
upwards.
5
The stipe has attained its
full length before the
spores are liberated.
The stipe elongates con-
siderably during libera-
tion of the spores.
For each fruit-body the five facts are correlated and only find
their full significance in reference to each other.
Doubtless, within certain limits, there has been a tendency for
the survival of those fruit-bodies which produce and successfully
liberate the maximum number of spores with the least expendi-
ture of fruit-body substance and energy. In both our types this
desideratum has been met in part by the production of central
tubular stipes, symmetrical radiate pilei, closely packed basidia,
tiny spores, and a much folded hymenium situated on the plate-
like gills. Further arrangements, however, in the two types
present marked differences.
In the Mushroom, adjacent basidia on any part of a gill
mature successively and shed their spores as soon as these are
ripe (cf. Plate I., Fig. 3). Every square millimetre of hy menial
surface on each gill, therefore, sheds a certain number of spores
each minute throughout the entire spore-liberating period of the
fruit-body. This necessitates that sufficient space shall be provided
between adjacent gills throughout their whole length by the time
212 RESEARCHES ON FUNGI
spore-discharge begins. These spaces are provided for a maximum
number of gills by the long axes of the latter becoming horizontally
outstretched at maturity (Plate I., Fig. 2 ; Plate IV., Fig. 25). In
order to fix the gills in this position (with their planes vertical),
the whole fruit-body must have the necessary rigidity. This is
given by the thick flesh.
In a fruit-body of Coprinus comatus there is much more gill-
FlG. 75. Amanita muscaria. Two fruit-bodies having the Ps/tlliota campcstris
type of spore-discharge. The gills are horizontally outstretched. The
space provided by the stipe beneath the pileus allows air-currents to
readily bear away the falling spores. In nature the tops of the pilei, which
bear white squamulae, are coloured a brilliant red. Photographed at
Sutton Park, Warwickshire, by J. E. Titley. About natural size.
surface in proportion to the whole mass than in a Mushroom.
The former, therefore, has solved the problem of developing the
maximum amount of spore-bearing hymenium with the least
possible expenditure of fruit-body substance and energy, much
more successfully than the latter (cf. Plate I., Figs. 1 and 2).
The Coprinus has such extremely thin flesh to its pileus that
it would be mechanically impossible for it to support its gills at
maturity with their long axes in the horizontal position. Associated
THE COPRINUS TYPE OF FRUIT-BODY 213
with the extremely reduced flesh, we find that the long axes of
the gills are almost vertical when spore-liberation begins. This
arrangement reduces the strain on the flesh to a minimum. The
pileus simply presses downwards on the stipe. When the gills
have become vertical at maturity they are then closely packed
together throughout their entire length except for their extreme
lower ends, where the change of shape of the pileus from the
barrel form to the bell form has caused them to separate. It
would be quite impossible for spores to be liberated from the
long vertical gills throughout every part of their whole length
simultaneously as in the Mushroom, for the gills are too close
together. If wide spaces were provided between them, not only
>vould this necessitate a large reduction in the number of the
gills, but a large number of spores would require to fall vertically
downwards between the gill-plates a distance of several centi-
metres. In that case, unless the gill-planes were quite vertical,
a considerable proportion of the spores would strike the hymenium
on falling, adhere there, and be wasted. Granted, therefore, that
the gills are closely packed and vertically extended at maturity,
it is obvious that a different arrangement for spore-liberation has
to be adopted to that found in the Mushroom. As a matter of
fact, as we have already seen, the Coprinus sheds its spores from
a narrow zone of spore- discharge which passes on each gill from
below upwards. At the zones of spore-discharge, the gills are
always sufficiently far apart (about 0*2 mm.) to permit of the
spores, when violently projected from their sterigmata, describing
the usual sporabolic paths unhindered. To enable the gills to
move apart from one another higher and higher up as the zones
of spore-discharge ascend upon them, the process of autodigestion
comes into play. This causes the removal of the spore-freed
portions of the gills and thus allows the fruit-body to gradually
open out and thereby separate the gills higher and higher up.
Without autodigestion it would be difficult to imagine how the
necessary interlamellar spaces could be provided at the moving
zones of spore-discharge. Toward the end of the period of spore-
discharge, the much shortened gills become horizontally out-
stretched like those of a Mushroom. At this stage, the pileus
2i 4 RESEARCHES ON FUNGI
requires to be disc-shaped in order to permit the parts of the
gills nearest the stipe to obtain the requisite spaces for spore-
discharge between them. The very thin flesh is also now quite
sufficient to support the much reduced burden of the gills in the
horizontal position.
During the process of spore-discharge, the stipe of Coprinus
comatus elongates considerably. It adds a number of centimetres
to its length and often becomes a foot long (Plate IV., Fig. 22).
As the fluid produced during autodigestion is gradually lost by
evaporation and dripping, the weight of the pileus, i.e. the load
which the stipe has to support, undergoes progressive reduction.
The higher the pileus can be raised with mechanical safety, the
better will be the chance of the spores escaping obstacles and
being carried off by the wind. It seems clear that the gradual
raising of the pileus by the elongation of the stipe is correlated
with the progressive diminution of the pileus weight. In the
Mushroom, on the other hand, the burden to be borne by the
stipe does not alter during spore-liberation. In keeping with this
we find that in this type of fruit-body the stipe attains its
maximum length before spore-discharge begins.
If the Coprinus and the Mushroom types be compared, I
think it must be admitted that the former is superior to the
latter in producing the maximum number of spores with the
minimum of fruit-body substance and energy. A Coprinus fruit-
body with its extreme reduction of flesh, vertical position of the
gills, successive ripening of the spores from below upwards, and its
beautifully regulated autodigestion, may be thought of as having
been evolved from a more generalised fruit-body of the Mushroom
type, with thick flesh, horizontal gills, irregular ripening of the
basidia, and absence of autodigestion. The special features of a
typical Coprinus fruit-body are bound up with its umbrella shape.
It seems to me that only after this had been attained could the
special Coprinus arrangements have been developed and become
effective. For this reason I regard the genus Coprinus as having
been derived entirely from a fungus having fruit-bodies of the
Mushroom type with central stipe and a symmetrically-placed,
gill-bearing pileus. At the present day there are no Coprini with
THE COPRINUS TYPE OF FRUIT-BODY 215
dimidiate form corresponding to Lenzites, &c. In my opinion the
explanation of this fact is not that such fruit-bodies have become
extinct but that they never existed.
Massee in his "Revision of the Genus Coprinus" states that
" the species of Coprinus differ from the remainder of the Agari-
cinefe in one important biological feature the deliquescence of
the gills at maturity into a liquid which drops to the ground,
carrying the mature spores along with it." This mode of spore-
dissemination he describes as "primitive and relatively imperfect,"
" as compared with the minute wind-borne spores of the remainder
of the Agaricineae." * Massee takes this mode of spore-dissemina-
tion as important evidence that "in the genus Coprinus we have
in reality thg remnant of a primitive group from which have
descended the entire group of Agaricine* having wind-borne
spores." Since my own investigations have now shown that the
spores of the Coprini are wind-borne, it must be concluded that
Massee's argument for the ancestral position of the Coprini is
based on an unfortunate misconception of the ecology of Coprinus
fruit-bodies. The arrangement for liberating spores into the air
by means of " deliquescence," instead of being primitive, appears
to be the most highly specialised in the whole group of Agaricineae.
The relative antiquity of the genus Coprinus seems to me to be
no easy matter to decide. However, at present I fail to find any
satisfactory evidence that the genus is to be regarded as closely
related to the one from which the other groups of gilled Agarics
have arisen. It seems more reasonable to regard it as a specialised
offshoot from a more generalised fungus of the Mushroom type.
1 G. Massee, "A Revision of the Genus Coprinus," Ann. of Bot., vol. x. p. 129 ;
also Text-Book of Fungi, London, 1906, p. 364.
CHAPTER XX
THE DISPERSION OF THE SPORES AFTER LIBERATION FROM
THE FRUIT-BODIES FALCK'S THEORY
WE have now gained some insight into the arrangements whereby
spores are enabled to escape from hymenomycetous fruit-bodies.
It still remains, however, to discuss the dispersion of the spores
in the outer air. Doubtless, in the narrow, blindly-ending tubes
of the Polyporese, and between the closely-packed gills of the
Agaricinese, the air is extremely still, so that the spores fall
approximately vertically downwards in it, in the manner already
discussed in Chapter XVII. If the air between the pilei and the
ground were also quite still, the spores would continue falling in
their vertical paths after emerging from the fruit-bodies, and
would strike the ground immediately below the basidia from which
they had been liberated. It is of interest to calculate the length
of time that would be required for the spores to reach the ground
in still air. The results of a few such calculations, together with
the data on which they are based, are given in the following
Table :
Approximate Length
Species.
Length of Stipe
between the B ise of
the Gills and the
Approximate
Average Velocity
of Fall of the
of Time required for
the Spores to Fall
from the Base of the
Ground.
Spores, i
Gills to the Ground in
Still Air.
Collybia dryophila . .
Psalliota campestris .
4. cm.
6 cm.
0'4 mm. per sec.
1'2 mm. per sec.
1 min. 40 sees.
50 seconds
Amanitopsis vaginata
7*5 cm. 3 mm. per sec. 25 seconds
Coprinus comatus . .
6-20 cm. 3 mm. per sec. j ^J^' 1 min ' 6
( Pileus growing "i
from a tree
Polyporus squamosus
-j trunk 4 metres 1 mm. per sec. ! 1 hour 6 mins.
above the
1 ground J
Estimated from the data given in Chaps. XV. and XVI.
THE DISPERSION OF THE SPORES 217
It is clear, from the results just given and from our knowledge
of the size of spores in Hymenoinycetes generally, 1 that for the
fruit-bodies of many species about a minute would be required for
the spores to fall from the gills to the ground. Even in the case
of Amanitopsis vaginata, where the spores are unusually large in
addition to being spherical, about half a minute would be necessary.
For fruit-bodies of Polyporus, Polystictus, Fomes, Stereum, Corticiurn,
&c., growing on tree-trunks or dead branches some metres high, the
ground would only be reached after the spores had been falling
through the air for a period of time of the order of an hour.
It seems certain that, owing to the alternation of day and
night and other meteorological causes, the air above the surface
of the earth is never quite still. The average speed of the air in
exposed situations is very considerable, amounting to miles an hour.
In woods and meadows, &c., where ground-fungi grow, the air-
movements are probably never less than some feet per minute,
and, as every one knows by experience, they are very frequently
much greater. Even when the air seems extremely still, so that
one cannot feel its motion and scarcely a leaf trembles on the
tallest trees, it is astonishing how complex and active are the
small convection currents and air-drifts that one may discover
near the ground, in gardens and woods, by the cautious liberation
of smoke or puff-ball dust. From what we know by experience
of air-movements, and from the calculations of the time that
would be required for spores to fall from their pilei to the ground
in perfectly still air, it seems to me to be an obvious conclusion
that the external air-currents, as a rule, are fully sufficient to
carry off the falling spores from beneath the pilei and to scatter
them broadcast. As a matter of fact in nature, unless a fruit-body
is confined by dense grass, loose leaves, or other natural obstacles,
one never finds any noticeable spore-deposit on the ground beneath
a pileus. For fruit-bodies of Stropharia semiglobata, Anellaria
separata, Coprinus comatus, or any other species growing in open
pastures, &c., it seems theoretically impossible that, if the wind is
blowing appreciably, any of the spores should settle on the ground
immediately beneath the pilei.
1 Chap. XIV.
218
RESEARCHES ON FUNGI
One of the chief functions of the stipe is undoubtedly to provide
a space usually one or more inches high between the under surface
of the pileus and the substratum on which the fruit-body may grow.
Owing to the very small rate of fall of the spores and the relatively
very much greater average horizontal speed of air-currents near the
ground, the space is amply sufficient, under normal conditions, to
permit of the falling spores being carried away from the fruit-body
and deposited at a distance from it.
Richard Falck 1 has put forward the theory that the fruit-bodies
FIG. 7<i. Semidiagrammatic sketch of a section in a field illustrating the manner in
which the spores of the Horse Mushroom (Psalliota arvensis) are liberated and
dispersed. A slight lateral movement of the air is supposed to be carrying the
spore-cloud away from the underside of the pileus. Reduced to .
are themselves specially adapted to produce air-currents for the
purpose of scattering the spores. His theory is founded on the fact
that fruit-bodies, when insulated, become distinctly warmer than the
surrounding atmosphere. In one of his experiments, he found that
the hy menial tubes of Polyporus squamosus, placed thickly together
in a carefully insulated chamber for ten hours, became 9 - 6 C.
warmer than similarly situated hymenial tubes which had previously
1 " Die Sporenverbreitung bei den Basidiomyceten und der biologische Wert
der Basidie," Beitriige zur Biologie der Pflanzen, Bd. IX., 1904, p. 1.
FALCK'S THEORY 219
been killed by heating. Falck believes that " the fruit-bodies pro-
duce heat not to raise their own temperature but to warm the layers
of air beneath the pilei." l He considers that the heat thus given off
creates convection currents in which the spores are borne away from
the pilei. In support of this, Falck has described experiments in
which spore-deposits were obtained from pilei which had been
suspended in closed glass vessels. He found that the spores were
carried up and down in the glass vessels so that they settled upon
ledges placed both above and below the pilei. Falck has followed
out his idea still further. After showing that the presence of
maggots leads to an appreciable increase in the temperature of
insulated pilei. he came to the following theoretical conclusions.
Tlje pileus flesh of large Agarics has become specially thickened and
laden with food substances for the purpose of feeding maggots. The
maggots respire actively and thus produce heat, which is added to
that resulting from the respiration of the pileus, and is made use of
for increasing the convection currents which bear away the spores
in the neighbourhood of the gills. We thus have a symbiotic
relationship between hymenomycetous fruit-bodies and flies.
It must be admitted that Falck's theory is a very ingenious one.
However, I am not sure to what extent we are justified in drawing
conclusions from the laboratory experiments as to what actually
happens in fields and woods. Proof has yet to be brought forward
that in nature the pilei become sufficiently warmed to produce
effective convection currents. If the ordinary air-currents in fields
and woods are never less than a few feet per minute, and are usually
much greater, it seems to me that they must be so active in carrying
away the spores from the fruit-bodies that the convection currents
arising from the very slightly warmed condition of the pilei can be
only quite insignificant, and therefore ineffective, in comparison.
From this consideration it seems that in nature the heat produced
by a pileus must be generally useless and unnecessary for the purpose
assigned to it by Falck.
When the wind is blowing, transpiration becomes active. Pos-
sibly the loss of heat from a fruit-body thereby occasioned, counter-
balances the gain by respiration. Falck's theory would be placed on
1 Loc. cit., p. 32.
220 RESEARCHES ON FUNGI
a much firmer basis if it could be shown that out in the open the
temperature of fruit-bodies becomes appreciably higher than that of
the surrounding atmosphere, but this has not yet been done. For
Polyporus squamosus (Fig. 1) and other fruit-bodies growing on
trees, where air-currents are never absent and the free space below
the pilei is usually great, for small or thin fruit-bodies such as those
of Mycena, Galera, Schizophyllum, Corticium, Stereum, and Poly-
stictus, and also quite generally for all fruit-bodies during weather
which is at all windy, the unimportance of any very slight warming
of the pilei seems to me to be obvious.
As a rule, in nature, it is impossible to see what happens to
spores on leaving the pileus. Otherwise a direct test might quickly
be applied to Falck's theory. However, in the case of Polyporus
squamosus, as described in Chapter VI., I have been able to see the
spore-clouds leaving a large fruit-body growing on a log. The log
was placed in a closed greenhouse, where the air was so quiet that
one could not feel that it was moving. As the spores emerged from
the hymenial tubes, they were carried along the underside of the
pileus in one direction by a very slow air-current moving at the rate
of a few feet per minute. The spore-clouds could be seen to drift
laterally to a distance of 2 metres from the fruit-body. Whilst
doing so, they were gradually broken up by small but very complex
convection currents, the presence of which was only revealed by the
spore-movements. As the spore-cloud moved outwards from the
edge of the pileus, it showed no tendency to pass upwards. In the
course of several hours, nothing happened to suggest that the fruit-
body was giving off so much heat that it produced convection
currents of importance in scattering the spores. It seems to me that
these observations are distinctly adverse to Falck's theory, for they
not only show that, even when the air seems very still, quite slow
air-currents due to external causes are of the greatest importance
in carrying the spores from beneath a pileus, but also that the con-
vection currents produced by a large pileus may be practically
inappreciable when this is not insulated.
However, it might be argued that the fruit-body was a solitary
one ; that Polyporus squamosus frequently produces from four to ten
sporophores in a densely imbricated cluster ; that the space between
FALCK'S THEORY 221
any two would become slightly warmed, and that, in consequence,
useful convection currents would be formed. However, since the
fruit-bodies are developed at some height on trees (cf. Fig. 1), any
such convection currents would most probably always be swamped
by more pronounced air-movements. If it be granted that there
is no special adaptation for producing heat in the fruit-bodies of
Polyporus squamosus, then the adaptation part of Falck's theory
becomes much weakened, for it was with this species that one of
the highest rises in temperature was obtained in the insulation
experiments.
The maggots which so frequently are to be found in fruit-bodies,
in most instances at least, seem to me to be in no way beneficent
to, the latter, and, in general, I am strongly inclined to look upon
them simply as harmful parasites. It would need a special investi-
gation to decide the matter, but it seems probable that of two
fruit-bodies equal in size, but one of them free from maggots and
the other badly infected, the former would produce and liberate the
greater number of spores. Even if they both liberated the same
number, we could still regard the maggots in the same light as some
gall-insects, i.e. as parasites which, as a rule, do no very appreciable
amount of harm, and for getting rid of which the plants concerned
possess no mechanism. Sometimes the harm done is quite obvious.
In a number of instances in the field, I have noticed fruit-bodies of
Amanita rubescens, &c., with the gills perforated and otherwise
damaged by maggots long before the spores had all been shed.
Occasionally, at an equally early period, the flesh of a pileus becomes
so weakened by the inroads of these animals that it can no longer
support the gills in the requisite vertical planes.
Doubtless, the heat which an expanding, maggot-free pileus
produces, like that arising in the rapidly opening capitula of Com-
positae, is due to respiration accompanying other active metabolic
changes. The gills in particular, whilst developing and setting free
their millions of spores, have a large amount of work to do. There
seems no reason to suppose that the fruit-bodies give rise to any more
heat than is necessitated by the processes concerned in rapid growth.
Probably puff-balls, which certainly do not use any heat which they
develop for scattering their spores, would become warmed on insula-
222 RESEARCHES ON FUNGI
tion in the same manner as the hymenomycetous fruit-bodies in
Falck's experiments. The metabolism which leads to the production
of a billion or more spores in a Giant Puff-ball in the course of a few
days, must be very considerable. For the present, at least, I am not
inclined to look upon the heat arising in the pilei as in any way
surprising in amount or as being more than incidental in character.
Although Falck's theory seems to me to require some modifica-
tion, and in any case to be of limited application, its promulgation
has certainly raised an important question. The fruit-bodies of
certain species of Boletus, Amanita, Paxillus, &c., have broad pilei
and comparatively short stipes; and they often come up, half
concealed in grass or loose leaves, in hollows, dense woods, or other
protected places. Here the air, immediately beneath the gills, on
quiet days must be at its stillest. We require to know whether
under such circumstances, owing to physical or metabolic changes
going on in the fruit-bodies, convection currents arise from the
latter capable of carrying the spores between the surrounding
obstacles and lifting them to such height that they pass into more
active air-currents in motion above the herbage or forest floor.
This ought to be determined by direct observation in nature.
Should such convection currents be discovered, it would then be
necessary to find out to what extent they were brought about by
radiation, transpiration, or the giving off of heat due to respiration.
If the air surrounding a fruit-body were ever quite still, any con-
vection currents arising from the pileus, in order to raise the spores
above the pileus, would require to have an average upward velocity
of 1-6 mm. per second according to the size of the spores.
Beam-of-light and other observations of my own have served
to corroborate Falck's discovery, that exceedingly faint convection
currents, such as one can never feel, are capable of transporting
the spores of Hymenoinycetes with astonishing ease. Even in
large closed beakers it is exceedingly difficult to reduce the air
to anything like real stillness. Small convection currents can
certainly be produced with a very small expenditure of energy.
Whether sufficient can be given off by a large fruit-body to be of
use under special circumstances remains to be determined. If
this should prove to be the case, we could draw the conclusion
FALCK'S THEORY 223
that millions and millions of spores, which otherwise might never
be dispersed, are as a matter of fact spread far and wide over fields
and woods.
If effective convection currents were given off by fruit-bodies,
then, doubtless, they might be increased by the presence of maggots
in the pileus and stipe. From this point of view the presence of
these animals in the sporophores of Amanita rubescens, &c., might
be of occasional advantage ; but it seems to me that, from the
data at our disposal, we are not yet justified in assuming a symbiotic
relationship between flies and Agarics.
We have now seen how easily the spores may be conveyed away
from the fruit-bodies by air-currents. The wind, when travelling
several miles an hour, must frequently carry the spores from a
fruit-body for very long distances. Owing, however, to their steady
fall at the rate of 0*5-5 mm. per second, sooner or later all spores
must reach the earth. The larger the spores, the sooner will
they settle. The big spores of many species of Coprinus will not
be carried on the average so far as the smaller spores of the Mush-
room or of Collybia dryophila. With the ultimate fate of the
spores after they have once settled we are not here concerned.
CHAPTER XXI
THE DISPERSION OF SPOKES BY ANIMALS COPROPHILOUS
HYMENOMYCETES SLUGS AND HYMENOMYCETES
THE fruit-bodies of the Hymenomycetes, as we have seen, exhibit many
beautiful arrangements both in structure and function, which enable
the spores to be liberated into the air beneath the hymenium in
such a manner that they may be carried away by the wind. A
comparative study of fruit-body organography in the numerous
and diverse species existing at the present day, permits us to
conclude with some certainty that the fruit-bodies of the Hymeno-
inycetes, at the beginning of their phylogenetic development, were
anemophilous, and that they remained so ever since. However, for
certain of the coprophilous fungi, or possibly for most of them,
animal agency is made of secondary use in bringing the spores
into a suitable situation for germination and further development.
Coprophilous Hymenomycetes. Certain species belonging to the
genera Coprinus, Panaeolus, Anellaria, and Galera are to be seen with
remarkable frequency upon the dung of horses and cattle, and one
may look for them in vain upon any other substrata. It seems
clear that they have become specialised for a coprophilous habit
of life. 1 The infection of the faeces may take place in two ways :
(1) By spores carried to them directly by the wind, and (2) by
spores which are first dispersed by the wind, which then settle,
and which are subsequently swallowed with herbage by the animals
concerned. That the first mode of infection is possible may be
1 Saccardo gives 757 species included in 187 genera as being coprophilous.
To this large number the Hymenomycetes contribute but few species as compared
with the Ascomycetes and Phycomycetes. Many coprophilous fungi, so far as is
known, are only found on dung. Species to the number of 708 are recorded as
living on the dung of Herbivora, 45 on that of Carnivora, and 4 on that of
Reptilia. Saccardo, Sylloge Fungorum, XH., Pars. I., 3, 873-902. Cited from
Massee and Salmon, Ann. of Bot., vol. xv., 1901, pp. 317, 322.
224
COPROPHILOUS HYMENOMYCETES 225
deduced from the fact that in the laboratory sterilised horse dung
can readily be infected with spores of various species of Coprinus :
the mycelium produced gives rise to fruit-bodies in the course of
a few weeks. In many cases at least, it is not necessary for the
spores to have passed through the alimentary canal of one of the
Herbivora in order to become capable of development. The second
mode of infection, in which the agency of the wind is supplemented
by that of animals, has been carefully investigated by several
observers. Thus Massee and Salmon, using antiseptic methods,
extracted the fsecal matter from the intestines of dead rabbits and
found that, when it was protected from aerial infection, there
developed upon it a considerable number of species of fungi, a
long list of which are recorded in their "Researches on Copro-
philous Fungi." 1 However, these authors were not successful in
obtaining any species of Hymenomycetes in this way ; but from
their observations it seems probable that the more frequent mode
of infection of the dung of horses and cattle in nature is indirect.
The spores are scattered broadcast over pastures by the wind : they
are then swallowed with grass by animals; they pass uninjured
through the alimentary canal, find their way into the fsecal matter
as soon as it is formed, and germinate in it immediately after it has
been deposited. By this means the spores come to be intimately
mixed throughout a faecal mass, so that its infection is much more
thorough and takes place sooner than could be the case with spores
merely settling upon its outer surface. No doubt, of the two modes
of infection the more highly specialised leads to a more rapid
development of new fruit-bodies.
Coprophilous Hymenomycetes, such as many Coprini, are
adapted to their environment in three special ways : firstly, in the
capacity of the mycelium to use the materials contained in dung
as food and to flourish when developing in faeces ; secondly, in
the spores being able to pass through the alimentary canal of
herbivorous animals uninjured ; and, thirdly, in the nature of the
fruit-bodies. The food specialisation has advanced so far that
a number of species of Coprinus, &c., judging from their distribution
1 Massee and Salmon, Ann. of Bot., vol. xv., 1901 ; vol. xvi., 1902.
P
226 RESEARCHES ON FUNGI
in nature, are dependent on the existence of particular herbivorous
vertebrates. It seems likely that the extinction of large Herbivora
in past geological ages has often brought about the extinction of
some of their associated fungi. With regard to the fruit-bodies
it may be pointed out that, as in Coprinus niveus, Panwolus
phalxnarum, Anellaria separata, and Galera tenera (cf. Figs. 25,
p. 68, and 32, p. 80), they usually have more or less campanulate
pilei situated on long and slender stipes. The latter, at least in
many Coprini and probably in the other coprophilous genera, are
at first heliotropic. This enables the compact young pilei to be
pushed out into the open from beneath or between balls of horse
dung, &c., so that afterwards, when the stipes change their
physiological properties and become negatively geotropic instead
of heliotropic, the pilei are placed in such a position that they
can expand and shed their spores into the air free from all obstacles.
The length and relative slenderness of a stipe are well suited to
enable that structure to thread its way outwards to the light by
a process of growth, and afterwards to make a geotropic curvature
by which the pileus can be brought into an advantageous position
for shedding its spores.
Slugs and Hymenomycetes. Many slugs find certain fruit-
bodies exceedingly palatable and often devastate them in a wood
to a surprising extent. One sometimes has difficulty in obtaining
a single intact specimen of Russula emetica, R. citrina, Amanita
muscaria, &c., even where they occur in considerable numbers.
The gills are particularly relished, but large pieces of the pileus
flesh are also frequently devoured.
Voglino 1 has made an investigation upon the relations exist-
ing between slugs and Hymenomycetes, and has arrived at a
very interesting conclusion. His chief observations were as follows.
The digestive tracts of slugs collected in some pine woods were
found to contain germinating spores of the following species:
Tricholoma humile, Mycena alkalina, Inocybe fastigiata, Lactarius
deliciosus, and species of Russula. Slugs were fed with fruit-bodies
of Russulse and Lactarii, and subsequently numerous germinating
1 P. Voglino, "Richerche intorno all' azione delle lumache e dei rospi nello
sviluppo di Agaricini," Nuovo Giornale Botanico, vol. 27, 1895, pp. 181-185.
SLUGS AND HYMENOMYCETES 227
spores of the species used were found in the digestive tracts of
the slugs and also in their faeces. When the faeces were placed
in hanging drops, the germ-tubes developed into a branched
mycelium. The spores of certain Hymenomycetes refused to
germinate in ordinary culture media, but germinated readily in
the fluid obtained from the digestive tract of a slug. An enclosure
was made around some ten specimens of Hebeloma fastibile which
were growing in the open, and four starved slugs were introduced
into it. In a few days the lamellae of all the fruit-bodies were
completely devoured. One of the slugs when dissected was found
to contain germinating spores of the fungus in its digestive tract.
The enclosure was kept moist with sterilised water and maintained
for about a year. At the end of this period it was observed that
the specimens of Hebeloma fastibile were much more numerous
in the enclosure than elsewhere in the neighbourhood. Toads
which were collected in some pinewoods were found to contain
germinating spores of species of Russula and Lactarius within
their alimentary canals. Some toads which were fed with slugs
were subsequently found to contain spores of Russula in an advanced
state of germination. Voglino came to the conclusion that the
propagation of fleshy Agarics, especially of Russulse and Lactarii,
is in a large measure due to slugs and toads which provide con-
ditions in their digestive tracts for spore germination.
Although it may be true that slugs help in the local dispersal
of spores in a wood or field and provide conditions for their
germination, these animals, owing to their slow rate of movement,
could scarcely act as agents in spreading fungus species from
wood to wood when these are separated by considerable distances.
That slugs find a fruit-body palatable is no proof that they are
the agents for distributing the species to which it belongs. In
this connection we may consider the case of Polyporus squamosus.
Its fruit-bodies are much relished by slugs. I have known them,
when young, so persistently visited and so voraciously eaten that
they have been utterly ruined and have ceased development.
Now in nature the trees on which the fungus occurs are usually
a considerable distance apart, rarely less than several hundred
yards and frequently much further. Moreover, the fruit-bodies,
228 RESEARCHES ON FUNGI
as a rule, are produced at some height from the ground. For a
slug, the infected trees are often several days' journey apart, and,
even if a slug were to travel directly from one to another, spores
swallowed on one tree would all be lost in the faeces before the
next had been reached. From a consideration of the distribution
of the fungus and of the movements of slugs it seems impossible
that these animals should materially help in spreading the species
from tree to tree. A similar argument might be applied to
Pleurotus ulmarius and many other species growing on trees,
as well as to such fungi as grow on the ground and are characterised
by the fruit-bodies developing sporadically at considerable distances
from one another. The Russulse, Amanitse, &c., exhibit all the
usual arrangements in their fruit-bodies for liberating the spores
into the air in such a manner that they may be carried off by the
wind. In the absence of slugs, hundreds of millions of spores
fall from the gills. We can scarcely suppose that spores thus
carried off by the wind have no chance of reproducing the species.
It seems probable, therefore, that the wind, even in the case of
the Russulse, is still by far the chief agent in spreading the fungi
from place to place.
The conditions necessary for the germination of the spores of
many of the higher fungi in nature are unknown. Voglino's
observations suggest that small herbivorous animals provide these
conditions much more often than has hitherto been supposed. It
was recorded in Chapter V. that a single Mushroom (Psalliota
campestris), with a diameter of 8 cm., produced 1,800,000,000 spores.
We are justified in supposing that a very large Agaric might
produce 4,000,000,000. If these were scattered uniformly in nature
there would be sufficient of them to provide one for every square
inch in a square mile. This calculation may perhaps serve to
indicate how widely dispersed the spores of one of the Hymeno-
mycetes may become, and how frequently they must be present
on grass, leaves, fruits, &c. Herbivorous birds, toads, slugs, insects .
worms, &c., must very frequently devour spores with their food.
Perhaps then, whilst in general the wind is the chief agent in
dispersing the spores of Hymenomycetes, in some species small herbi-
vorous animals provide the conditions for their germination and the
SLUGS AND HYMEXOMYCETES
229
production of a mycelium. It seems not at all impossible, for
instance, that the spores of a species of Russula or Lactarius might
be carried several miles from one wood to another, and that after
settling they might be eaten with other vegetation by slugs : the
spores might then germinate in the fceces of these animals, and
the mycelium thus produced might make its way into the
vegetable mould of the forest floor.
The fruit-bodies of certain species of Hymenomycetes appear
to be protected from destruction by slugs owing to the presence
in their cells of nauseous or distasteful substances. In the
summer of 1904 I began to investigate the relations of slugs
to fungi, but unfortunately, owing to my removal to Winnipeg,
/the work was interrupted, and I have not found opportunity up
to the present to resume it. Such results as were obtained five
years ago are embodied in the accompanying Table. The obser-
vations on Omphalia, Hypholoma, and Cantharellus were kindly
made for me by Miss J. S. Bayliss. Before each test the slugs
were starved for about two days.
Slugs and Hymenomycetes.
Species of Slugrs.
Fungus Fruit-bodies.
Limax
Arion
Auriolimax
maxiinus.
1 subfuscns.
agrestis.
Armillaria mellea
i E
E
E
Russula emetica .
E
E
E
Amanita muscaria
1 E
E
E
Amanita rubescens
E
E
N
Omphalia umbellifera .
i E
E
Lactarius rufus .
; S
S
Lactarius glyciosmus .
Hygrophorus pratensis
Hygrophorus virgineus
Hypholoma fasciculare
Laccaria laccata .
S
i S
N
N
N
N
N
N
N
Cantharellus lobatus .
N
E = fruit-bodies readily eaten ;
S = fruit-bodies slightly eaten and evidently disliked ;
N = fruit-bodies not eaten at all, so far as could be seen, the slugs preferring
starvation to feeding ;
= no experiment.
230 RESEARCHES ON FUNGI
The results just given indicate that, whilst species of Armillaria,
Russula, Amanita, and Omphalia are relished by the slugs tested,
species of Lactarius, Hygrophorus, Laccaria, Hypholoma, and
Cantharellus are disliked to a greater or less extent.
Lactarius rufus to our taste is exceedingly acrid, and its
peculiar latex may well be the cause of its being but very slightly
eaten by hungry slugs. In nature, among thousands of fruit-
bodies of this species, I have very rarely found one slug-eaten,
and then very slightly. Once a specimen was noticed which,
from the slime left all over the gills, had evidently been visited
by a slug, but which had not been attacked ; whereas fruit-
bodies of Russula citrina close by had been seriously damaged.
This seems to afford distinct evidence that the one species is
chemically protected from slugs and that the other is not.
Lactarius glyciosmus contains a peculiar aromatic substance, and
it may be this which causes the fruit-bodies to be left uneaten
by Agriolimax agrestis.
The fruit-bodies of most species of Hygrophorus are glutinous
or viscid and their gills are waxy. Possibly it is their physical
nature which renders them distasteful to slugs. The exact causes
which render these and other fruit-bodies, such as those of
Hypholoma fasciculare and Laccaria laccata, inedible, require
further investigation.
Mere acridity of itself is not sufficient to cause a fungus to be
rejected by slugs. Every one is agreed that the fruit-bodies of
Russula emetica are very acrid; yet all three species of slugs
tested eat them with avidity.
Slugs can feed upon a number of fruit-bodies which are
poisonous to man. Thus Amanita muscaria was eaten vora-
ciously by all three of the slugs tested and without any ill effects
to them. Amanita phalloides is one of the most poisonous
of fungi, and yet in nature one may often find slug-eaten fruit-
bodies of this species. It is evident that muscarine, phalline, and
other toxines present in species of Amanita have no protective
significance so far as slugs are concerned.
PART II
SOME OBSERVATIONS UPON THE DISCHARGE AND DIS-
PERSION OF THE SPORES OF ASCOMYCETES AND
OF PILOBOLUS
CHAPTER I
THE DISPERSION OF SPORES BY THE WIND IN ASCOMYCETES
PUFFING THE PHYSICS OF THE ASCUS JET IN PEZIZA THE
FIXATION OF THE SPORES IN THE ASCUS OF PEZIZA REPANDA
COMPARISON OF THE SIZES OF WIND-BORNE SPORES IN
ASCOMYCETES AND HYMENOMYCETES THE HELVELLACEyE.
NOT only in the Hymenomycetes, but also in many other fungi,
beautiful adaptations are to be found by which the spores are
suitably dispersed, but- in most instances the mechanism involved
still awaits a careful analysis from the point of view of physics.
In the majority of the Ascomycetes, the ascus is an explosive
mechanism of considerable power, and it often shoots out its spores
to a distance of one or several centimetres, thus causing them to
become effectively separated from the sporocarp. It was pointed
out in the first chapter of Part I. that the profound differences
between Hymenomycetes and Ascomycetes in the position occupied
by the hymenial surfaces, and in the structure of the fruit-bodies,
are correlated with the equally profound differences between
basidia and asci as spore-discharging mechanisms.
The dispersal of ascospores after ejection from the ascus appears
in many cases to be brought about either by the wind or by her-
bivorous animals. I regard it as a distinct matter of importance
which of these two means of dispersal is employed, for each of
them is associated with a particular type of ascus. As examples
of Ascomycetes with wind-dispersal may be mentioned Gyromitra
esculenta, Morchella gigas, Bulgaria polymorpha, and Peziza
aurantia, whilst Ascobolus immersus and Saccobolus may be
regarded as representing those forms which are spread by her-
bivorous animals. It is probable that there are some species of
Ascomycetes which have an intermediate type of spore-dispersal,
corresponding to that associated with coprophilous Hymenomycetes,
in which the spores are first scattered by the wind and subsequently
234 RESEARCHES ON FUNGI
become redispersed by herbivora. In these species it is to be
expected that the structure of the ascus would be correlated with
wind-dispersal.
The Dispersal of Spores by the Wind in some Ascomycetes.
According to Falck, 1 in Gyromitra esculenta one of the Helvel-
lacese the spores, after being shot out of the ascus, become
separated from one another and settle singly; and I have noticed
a similar phenomenon in Bulgaria polymorpha (Wettst.). Doubt-
less, in both these species, the spores, which are no larger than
those of many Hynienomycetes, are carried away from the fruit-
bodies by the wind.
Plowright 2 watched the discharge of the spores of Morchella
gigas one evening with the aid of an oblique beam of sunlight.
He observed that the head of each Morel was surrounded by a
cloud of spores extending 3 or 4 inches around it. He states
that "This cloud could only be seen in the oblique light against
a dark background. When acted upon by a gentle current of
air, such as would be produced by gently waving the hand, it
swayed to and fro without manifesting any tendency to become
dispersed. The component sporidia were in constant motion,
rising and falling and circling about, as if the law of gravity
were a myth, existing only in the imagination of philosophers.
When the cloud was quite blown away by a more powerful air-
current, it in the course of a few seconds reformed. The contents
of each ascus could be seen to be separately ejected in a minute
jet consisting of a limited number of sporidia, which speedily
became lost with the others forming the cloud." From this
description it seems evident that the cloud of spores which forms
above a fruit-body of a Morchella is very similar to that which
forms under the pileus of a Hymenomycete, such as a Mushroom
or a Polyporus. In both clouds the spores are separated from
one another and fall so slowly through the air that they can
readily be carried off by very slight air- currents.
1 R. Falck, " Die Sporenverbreitung bei den Basidiomyceten," Beitrage zur Biol.
der Pftanzen, Bd. IX., 1904, p. 51.
2 C. B. Plowright, "On Spore Diffusion in the larger Elvellacei," Grevillea,
vol. ix., 1880-81, p. 47.
ASCOMYCETES AND WIND DISPERSAL
235
We shall now consider the phenomenon of the separation of
the spores from one another, just after discharge from the ascus.
That this actually occurs in some and probably in very many
species seems to me to be conclusively proved by (1) The definite
observation by Falck x that the spores of Gyromitra esculenta
settle singly, and a similar observation by myself upon Bulgaria
polymorpha ; (2) the just quoted description by Plowright of
spore-discharge in Morchella gigas ;
and (3) some observations upon ':
the discharge of individual asci of
Peziza which have been made by
my laboratory attendant, Mr. C.
W., Lowe, and myself. Mr. Lowe
has informed me that h& watched
the discharge of spores from a
fruit-body of Peziza aurantia be-
neath an electric lamp with a
lens. He states that each indi-
vidual ascus jet appeared to break
up at a distance of from 2 to 2*5
cm. from the top of the fruit-body,
and that in one instance on the
breaking up of a jet, he was able
to count six separated spores.
With the help of my beam-of-light method I have fortunately been
able to repeat and extend these observations.
A fruit-body of Peziza repanda (Fig. 77) came up upon horse
dung in the laboratory. When ripe, it was placed upright in the
middle of a covered glass jar, 6 inches high and 4 inches in
diameter ; and a strong beam of light was directed through the
air immediately above the hymenium. 2 I then observed that
the asci discharged their contents into the air successively, at
intervals of a few seconds. Although in the course of two or
three hours I watched the discharge of several hundred asci, in
no case was I able to detect an ascus jet taking its upward flight
FIG. 77. The discharge of spores from
Peziza repanda, f, section of a fruit-
body covered above with the hymenium
A and supported by a stipe with a root-
ing base ; d, horse dung ; g, glass base
of the culture dish. Above the hyme-
nium are shown several groups of eight
spores as seen in a concentrated beam
of light immediately after their dis-
charge from the asci. Natural size.
1 R. Falck, loc. cit.
2 Cf. Part I., Chap. VII.
236 RESEARCHES ON FUNGI
into the air. The discharged contents of each ascus always made
their first appearance as eight spores which had already separated
from one another, and which were falling very slowly downwards
at a distance above the hymenium of about 2-3 cm. (Fig. 77).
The sudden bursting into view of the eight glistening and falling
particles against a black background forcibly reminded me of the
sudden illumination of the sky at night by a shower of brilliant
points of light produced by an explosive rocket. The eight spores
of each ascus, at the moment of their appearance in the beam of
light, usually formed a more or less regular vertical series in which
FIG. 78. Semi diagrammatic sketch of a section through a fruit-body of Feziza rcpanda
whilst discharging its spores. The spores are shot up to a height of 1-2-5 cm.
above the hymenium and are then carried off by the wind. Natural size.
the highest spore was several millimetres from the lowest. It was
observed that very slight air-currents were sufficient to carry the
separated spores round and round in the air contained within the
glass jar. It can scarcely be doubted, therefore, that the spores
of the Peziza are dispersed in nature by the wind in the same
manner as those of Hymenomycetes. It is interesting that the
cloud of spores produced by the Peziza comes into being, not
immediately above the hymenium, but at a distance of 2-3 cm.
above it. This enables horizontal air-currents which are almost
universally found above the surface of the ground to carry away
the spores before they have time to fall back on to the fruit-body
from which they have been discharged (Fig. 78).
PUFFING 237
Puffing. The normal method of spore-discharge from Peziza re-
panda under natural conditions is probably a more or less successive
discharge of ripe asci, the spore-discharge period lasting for some days.
A similar gradual emptying of the asci has been observed in other
Peziza?, in Helvella, Morchella, Bulgaria, Exoascus, &c. x When a
fruit-body of Peziza repa-nda was left undisturbed for some hours in
a damp-chamber it ceased to liberate its spores. The beam of light
showed that none of the asci were discharging their contents.
However, when the glass plate covering the culture vessel was
raised and the hymenium was rubbed with a match-stick or other
rod, a considerable number of asci burst almost simultaneously and
spore-discharge continued for at least an hour. According to De
Ba^ry, the simultaneous discharge of a large number of asci the
phenomenon known as " puffing " may be caused in Peziza
acetabulum, P. sclerotiorum, and Helvella crispa by shaking a fruit-
body, or by suddenly allowing a fruit-body which has previously
been kept in a damp-chamber to come into contact with dry air. 2
He further found that the bursting of isolated ripe asci when lying
in water can be brought about " by exposing them to the operation
of agents like alcohol and glycerine, which withdraw their water." 3
He came to the conclusion that loss of water causes puffing " by
altering the state of tension in each ascus either by lessening the
expansion of the lateral walls and so increasing the pressure of the
fluid contents on the place of dehiscence, or by lessening the power
of the place of dehiscence to resist the pressure which remains
unaltered." 4 Massee 5 has pointed out that this explanation is not
entirely satisfactory, " as fungi will often puff, after lying in a room
for some hours, if moved." In Peziza rej)anda I have found that
mere rubbing without change of atmospheric conditions was suffi-
cient to cause some of the asci to burst. The simplest explanation
of these two observations seems to be a mechanical one. One may
suppose that at any one time the hymenium of a mature sporocarp
contains a number of asci which have almost reached the critical
1 De Bary, Comparative Morphology and Biology of the Fungi, Mycetozoa, and
Bacteria, English translation, 1887, p. 89.
2 Ibid., p. 90. 3 Ibid. * Ibid.
6 G. Massee, British Fungus Flora, 1895, vol. iv. p. 4.
238 RESEARCHES ON FUNGI
bursting stage of development, and that the rubbing or shaking
simply causes the premature bursting of a few such asci owing to
their equilibrium having been mechanically disturbed. According
to this theory, the discharge of the asci may be likened to the
premature bursting of the capsules of Impatiens, which one may
bring about by slight alternate compression and relaxation with the
fingers. However, it seems to me not unthinkable that the rubbing,
shaking, or moving of a fruit-body may serve to stimulate the proto-
plasm in the asci in some way so that it reacts in such a manner as
to cause the asci to explode.
I have tried the effect of various chemical substances upon the
discharge of ripe asci lying in water, and I have been unable to
confirm De Bary's statement that bursting of the asci can be brought
about by agents which withdraw water from them. Sections through
the ripe hymenium of Peziza repanda were cut and mounted in
water on microscope slides in the usual manner. In order to test its
effect upon the asci, a solution of a salt or other substance was then
run under the cover-glass gradually. It was found that strong
solutions of glycerine, sodium chloride, potassium nitrate, and grape
sugar did not cause explosions to occur. The sodium chloride,
potassium nitrate, and grape sugar led to considerable contraction
in the volume of the asci, so that it is evident that mere withdrawal
of water from asci is not sufficient to cause them to explode. On
the other hand, solutions of iodine, mercuric chloride, silver nitrate,
copper sulphate, sulphuric acid, acetic acid, and alcohol gave rise to
very marked puffing. A very active discharge of spores took place
as soon as the asci came well into contact with these substances. In
a number of instances practically all the living asci discharged their
spores, and a heavy spore-deposit collected a short distance in front
of the ascus mouths. The seven substances last named are all
poisonous, whereas the four which do not cause puffing are non-
poisonous. I was therefore tempted to draw the conclusion that
poisonous substances cause puffing, whereas non-poisonous ones do
not. However, further experiment showed that this rule does not
hold universally. Strong sodium hydrate poisons the asci without
causing them to explode. When a solution of this substance was
PUFFING 239
brought into contact with the preparation, after a time the asci one
by one contracted suddenly without discharge. Evidently their
turgidity became lost owing to the death of the protoplasm lining
the ascus wall. Sodium carbonate also did not cause ascus discharge,
although the asci died from its effects. Up to the present, therefore,
it seems that non-poisonous substances and alkalies do not cause
puffing, whereas poisonous substances, excluding alkalies, do. Why
alkalies should behave differently to other poisonous substances
seems for the present inexplicable.
In one experiment an ascus was caused to contract considerably
with potassium nitrate. It did not explode. It was then restored
to its former size by placing it in water. When brought into contact
with iodine dissolved in water, it immediately exploded without
undergoing any preliminary measurable decrease in volume. This
observation will serve to emphasise the difference in action between
a neutral salt which merely withdraws water from an ascus, and a
non-alkaline poisonous substance which affects the protoplasm.
Asci w r hich have contracted in volume owing to loss of water on
treatment with a strong solution of a neutral salt, may be caused to
explode when brought into contact with iodine. The explosions
under these conditions are naturally comparatively weak, and the
spores shot out from the asci travel but a very short distance from
the ascus mouth.
The experiments just recorded seem to me to suggest that the
bursting of ripe and expanded asci is not brought about by an
increase in the pressure of the cell-sap upon the ascus lid, but rather
by an alteration in the strength of attachment of the ascus lid to the
rest of the ascus wall. We may regard the protoplasm at the end of
the ascus as specially entrusted with the work of loosening the
attachment of the ascus lid, as its final duty. By suitable stimula-
tion of this guardian protoplasm, the attachment may be indirectly
loosened and thus an ascus explosion brought about. Possibly the
necessary stimulus can be given mechanically, as when a sporocarp
is caused to puff by mere moving or shaking; possibly it may be
given by a sudden withdrawal of water from the end of the ascus, as
when a sporocarp is caused to puff by suddenly allowing it to come
240 RESEARCHES ON FUNGI
in contact with dry air ; but it seems certain that it can be given by
chemical means, as when an ascus is caused to explode when treated
with silver nitrate, mercuric chloride, alcohol, and certain other
poisonous substances. Where there is a gradual emptying of ripe
asci, as, according to De Bary, occurs in Bulgaria, Exoascus, &c.,
probably the activity of the guardian protoplasm is controlled by
stimuli arising from internal developmental changes taking place in
the ascus as a whole.
At present there does not seem to be any evidence that puffing
takes place under natural conditions, and it would therefore be
fruitless to discuss whether or not the phenomenon has any useful
biological significance. It may be added that puffing, when observed
in still air with the aid of a beam of light, is a beautiful exhibition
of sporocarp activity. It may be likened to the grand finale of
sky-rockets in a pyrotechnic display.
The Physics of the Ascus Jet in Peziza. From my obser-
vations upon the discharge of individual asci, it is clear that
the spores contained within an ascus jet become separated from
one another within a fraction of a second, between the time that
they leave the ascus mouth and the time that they suddenly
appear as eight separated particles in the beam of light. We
shall now inquire into the nature of the forces which serve
to detach the spores from one another during their ascent into
the air.
The ascus wall contracts during the ejection of the ascus jet,
so that the ascus volume becomes reduced to about one-half
(Fig. 79, E and F). The nature of the contraction affords a
strong argument for the belief that the pressure exerted upon
the ascus contents is greatest at the beginning of the discharge,
and that it diminishes continuously and rapidly during the dis-
charge, so that it finally becomes zero when the discharge has been
completed. The ascus jet on leaving the ascus mouth may be
regarded as a more or less cylindrical column of fluid containing
eight spores situated in a row. Owing to the nature of the ascus
contraction, it seems almost certain that the front end of the
ascus jet must be shot outwards with the greatest velocity and
the rear end with the least. The whole jet after its emission
THE PHYSICS OF THE ASCUS JET 241
will tend to become elongated. The first spore will have a
r 1
s-\
i
n\
5
I
E
V
U
FIG. 79. Peziza rcpanda. A, a young unripe fruit-body. Natural size. B, an older
expanded fruit-body which was discharging spores. Natural size. C, a vertical
section through the disc of B showing the hymenium h, the subhymenium s, and
the excipulum e with an external brown layer 6. Magnification, 40. D, two
septate paraphyses with clavate terminal cells. E, a ripe ascus containing eight
spores which are loosely attached to one another and are suspended in a subterminal
position by a filament probably composed of protoplasm. F, a contracted ascus
just after the spores have been discharged. G, the end of an ascus in which only
partial spore-discharge had taken place. A spore was making its exit endwise
through the ascus mouth. H, eight separated spores as seen near the mouth of an
ascus just after discharge into a fluid medium. The unilateral gelatinous invest-
ments, shown within the ascus at E, have now become very much swollen. I, a
spore which after discharge had fallen back on to the hymenium and had then
germinated. The germ-tube gave rise to two clavate conidiophores bearing minute
conidia. D-I magnification, 317.
higher velocity than the second, the second a higher one than
Q
242 RESEARCHES ON FUNGI
the third, and so on. It seems to me very probable that it is
the considerable differences in the initial velocities given to the
different spores upon their discharge which is the chief factor in
separating the spores from one another during their upward flight
into the air. There is, however, another factor which must be
concerned with the breaking up of the ascus jet, namely, surface
tension.
It has been found both by mathematics and experiment that
the equilibrium of a free cylinder of any liquid, under the in-
fluence of surface tension only, becomes unstable as soon as the
length exceeds TT times the diameter ; and it is regarded as a
necessary consequence of this that such a cylinder, if once realised,
will spontaneously split into as many equal and equidistant spheres
as TT times the diameter is contained in the length. 1
Thus if n be the number of drops,
I the length, and
d the diameter of the cylinder,
the law of segmentation is expressed by the formula
From this formula we can calculate that, if the length of a
cylindrical column of fluid is twenty-five times the diameter, the
column will break up under the influence of surface tension into
eight separate drops. It seems to be a simple inference from this
that, if in a minute cylinder of this kind there were placed eight
equidistant solid spheres with diameters equal to the diameter
of the cylinder, then the cylinder would break up in such a
manner that each spherical body would become separated from
its neighbours and enclosed within a film of fluid. The ascus
jet must be at first essentially a cylindrical liquid column con-
taining solid oval nuclei at intervals. Probably the spores are
ejected end-wise through the contractile ascus mouth so that
they come to have their long axes in the same direction as the
long axis of the jet. As the jet becomes elongated, owing to its
1 A. M. Worthington, "On the Spontaneous Segmentation of a Liquid An-
nulus," Proc. of the Roy. Soc., vol. xxx., 1879-80, p. 49.
THE PHYSICS OF THE ASCUS JET 243
parts, beginning with the front end, having been ejected from
the ascus mouth with successively diminishing velocities, it will
reach a stage when the relationship of its length to its diameter
becomes such that surface tension must cause it to break up
into eight separate parts. Each tiny column of fluid, which at
first must connect adjacent spores, will become unstable when
its length exceeds three times its diameter, and upon slight
further elongation it will snap into two in the middle. Since
the eight spores ejected from an ascus, on their first appearance
in the beam of light, usually form a more or less vertical series
in which the highest spore is several millimetres above the lowest,
it seems to me probable that the segmentation of the ascus jet
takes place almost immediately after it has left the ascus
mouth.
If the ascus is regarded as a mechanism for discharging a jet
in such a manner that the jet elongates and becomes segmented
by surface tension into eight separate parts, each part containing
a spore, then the structure of the ascus becomes more intelligible.
The long cylindrical form of the ascus and the size of the spores
are such that the spores must lie in a single row one behind the
other. This arrangement favours the production of a long jet in
which the spores are situated in a row. The oval shape of the
spores, and the fact that their long diameters are wider than the
ascus mouth, must necessitate their being ejected through the
ascus mouth end-wise (Fig. 79, G). Whilst the first half of a
spore is passing through the contractile ascus mouth, the velocity
of movement of the spore is probably slightly diminished; and
whilst the last half is passing, the velocity is probably slightly
increased. This would lead to a separation of the spores in the
jet at the very beginning of its formation. The advantage in an
ascus containing a number of spores instead of one is probably
to be found in the fact that less energy would be required to
shoot up several spores from one ascus at one time than would
be required to shoot up the same number of spores if each were
contained in a separate ascus. The production of exactly eight
spores in each ascus rather than a few more or less may have
been determined in the first place by convenience in nuclear
244 RESEARCHES ON FUNGI
division. The advantages accruing to a fungus from the separation
of the spores of an ascus after they have been cast up into the
air are: (1) The increase in the number of separate infecting
particles which the fungus can produce, and (2) the splitting up
of the mass of the ascus jet. The separate parts of the ascus jet
must each fall considerably more slowly than the ascus jet would
do if it remained undivided and contracted into a ball, for,
according to Stokes' Law, the terminal velocity of fall of a
microscopic sphere varies directly as the square of the radius.
The smaller the rate of fall of a particle, the further can it be
transported by the wind before settling. The separation of the
ascus spores from one another is therefore favourable to their
dispersal by air-currents.
It has been shown that the spores of Hymenomycetes, when
falling in air unsaturated with water vapour, dry up within a
few seconds after leaving the hymenium, and that, in conse-
quence, their rate of fall often becomes considerably reduced. 1 In
some instances it was found that the initial terminal velocity
becomes reduced to one-half or one-third according to the degree
of humidity of the air. Doubtless, in Ascomycetes, the small
film of liquid on the exterior of each separate spore, and also the
spore itself, dry up in unsaturated air within a few seconds after
the spore has been discharged. Evaporation, by decreasing the
size of the falling particles, must indirectly decrease their rate of
fall, and therefore in the end be advantageous for the dissemination
of the spores by the wind.
The Fixation of the Spores in the Ascus of Peziza Repanda.
In order to permit of the efficient ejection of the ascospores, it is
necessary that they should be situated at the distal end of the
ascus ; for the ascus is an apparatus which squirts out only about
one-half of its contents the half nearest the ascus mouth. Zopf
has shown that in many cases the spores are retained in the
expanded end of the ascus by a special apparatus of attachment:
the uppermost spore in some Sordariese is attached to an inwardly
directed process produced from the membrane at the ascus
1 Part I., Chap. XVI.
FIXATION OF SPORES IN THE ASCUS 245
apex. 1 De Bary 2 in this connection said, " Similar apparatus may
perhaps frequently be in use especially in the Pyrenomycetes. ... In
many cases, especially in the Discomycetes, there is no such apparatus
present, the spores being suspended in the fluid of the ascus. The
spores must have nearly the same specific gravity as the fluid;
if not, they would change their position as the ascus changes its
inclination, which they do not do. Most, if not all, spores produced
in asci sink in pure water; the fluid contents of the ascus must
therefore be of greater specific gravity than pure water, since it
holds in suspension bodies of greater specific gravity than water.
If increase in the amount of the fluid contents causes the apical
portion of the ascus to stretch more than the other parts, currents
must be set up in the fluid in the direction of the apex and continue
as long as the expansion continues, and push the spores therefore
permanently towards the apex. The arrangements of the spores
may then be affected by special directions in the currents which
we cannot at present determine, as well as by the conditions of
space noticed above." This hypothesis of currents does not seem
to me to be at all adequate to explain the position of the ascospores
at the end of the ascus. There are various objections of a physical
character which may be made to it, but it does not appear necessary
to discuss them. On the other hand, I shall show that in Peziza
repanda the position of the spores is attained by other than hydro-
static means.
In Peziza repanda the eight spores occupy a subterminal
position, so that there is a short space between the first spore and
the ascus lid (Fig. 79, C and E). Schroter 3 has figured an ascus
of P. repanda with the first spore in contact with the lid. This
arrangement may often be seen in dead asci but never in living
ones. Each spore possesses a firm cell-wall, and in addition is
coated on one side with a thin oval gelatinous investment
(Fig. 79, E). These investments appear to serve the purpose of
attaching the spores to one another so that they cannot slip
1 Zopf, Sitzsber. d. Berliner naturf. Freunde, Feb. 17, 1880. Cited from de Bary's
Comparative Morphology and Biology of the Fungi, etc., English translation, 1887, p. 88.
2 De Bary, loc. cit.
3 J. Schroter, " Pezizinese," in Die naturlichen Pflanzenfamilien, by Engler and
Prantl, Teil I., Abteil. 1, p. 183, printed 1894.
246 RESEARCHES ON FUNGI
apart. The group of eight spores is attached to the ascus lid
by means of a fine, somewhat granular filament which has the
appearance of a protoplasmic bridle. A row of granules can be
seen passing down the middle of the gelatinous cap of each spore,
so that it seems probable that the filament is continued downwards
from the topmost to the bottom-most spore (Fig. 79, E). It seems
not unlikely that the row of spores is fixed to the sides of the
ascus by other protoplasmic bridles, but I have not been able to
discover them. The fine terminal filament is very transparent, and
it may be on this account that it has hitherto been overlooked.
It can be made more prominent by treatment with 1 per cent,
corrosive sublimate. From the foregoing, it is clear that in Peziza
repanda the spores are not freely floating in the ascus sap as
de Bary supposed was the case in Discomycetes generally, but
are carefully anchored in position by one or more special proto-
plasmic filaments. This being so, one can easily understand how
it is that the spores keep near the end of the ascus during the
stretching period, and there is no need of the current hypothesis
to explain the phenomenon. Lack of material has prevented me
from investigating the extent to which protoplasmic bridles are
used for anchoring the spores in the asci of Discomycetes generally,
but it seems probable that this method of spore fixation will be
found to be of very common occurrence.
There can be no doubt that in Peziza repanda the eight spores
in each ascus are attached together. They always appear to be in
intimate contact with one another, but that they are really attached
to one another may be shown in the following manner. A section
through the hymenium (Fig. 79, C) is mounted in water. A strong
solution of grape sugar or sodium chloride is then run under the
cover-glass of the preparation, with the result that the turgor of
the asci becomes reduced. When this has happened a solution
of iodine is run under the cover-glass. The iodine on coming in
contact with the asci causes them to explode, but since the pressure
of the ascus sap has been reduced, the explosions are comparatively
weak. Sometimes the spores are not all shot out of the ascus
(Fig. 79, G), and in some cases they are only just ejected from the
ascus mouth. When the latter has happened, one sometimes sees
FIXATION OF SPORES IN THE ASCUS 247
the ejected spores placed end to end, one behind the other, so as
to form a continuous chain. It is highly improbable that a group
of ejected spores should form such a chain if they were not really
attached together.
When a section through the hymenium of Peziza repanda is
mounted in water, the asci are fully turgid. If such asci are
caused to explode by bringing a solution of iodine into contact
with them, the spores are discharged to a distance from the ascus
mouths about equal to the length of the asci. When vigorously
discharged in this manner, the eight spores are shot out so quickly
that one can see nothing of them as they pass through the fluid
medium. The eight spores suddenly come into sight in front of
the ascus which has discharged them. They are then not travelling
horizontally but merely sinking in the fluid. On their first appear-
ance they are all separated from one another in the manner represented
in Fig. 79, H. The very transparent, unilateral, gelatinous cap on
each spore then swells up considerably, doubtless owing to the
absorption of water. Running down the middle of each cap is
a row of granules, which are doubtless the same as those shown
in Fig. 79, E, and therefore the remains of the suggested extension
of the protoplasmic bridle over the spores.
The attachment of the eight spores of an ascus to one another
in Peziza repanda is not a firm one like that in Ascobolus imniersus
(cf. Figs. 81 and 82), but only a very loose one just strong enough
to hold the spores together before discharge, and therefore of use
in aiding them to take up a favourable position in the ascus,
but weak enough to be easily broken down at the moment when
the ascus ejects its contents. In all probability, the snapping of
the spore chain* into eight parts is due to the different spores
receiving different velocities during their ejection, and takes place
as the ascus jet is elongating whilst leaving the ascus mouth.
One further point concerning the spores of Peziza repanda
may here be mentioned. When a fruit-body is confined in a
small closed chamber, many of the spores, after being cast up
into the air, fall back again on to the hymenium. Under moist
conditions such spores often germinate and produce conidia, as
shown in Fig. 79, I.
248
RESEARCHES ON FUNGI
Comparison of the Sizes of Wind-borne Spores in Asco-
mycetes and Hymenomycetes. The size of wind-borne spores,
which is so important a factor in determining their rate of fall,
is doubtless adapted to the spread of the spores by such air-
currents as ordinarily occur above the surface of the ground.
In this connection it is a distinctly interesting fact that although
Ascomycetes produce and then liberate their spores into the air
in a very different manner to that of Hymenomycetes, yet in
both groups of fungi the order of magnitude of the wind-borne
spores is the same. Evidence supporting this statement is given
in the following Table, where the sizes of the spores of a few
Ascomycetes which make use of the wind for dissemination
are compared with the sizes of the spores of a few well-known
Hymenomycetes. In each series the spores are arranged accord-
ing to the magnitude of their short diameters. This arrange-
ment has been adopted because the rate of fall of spores, and
therefore the ease with which they can be transported by air-
currents, is chiefly determined by the size of their short diameters
and not by that of their long diameters, since spores tend to fall
with their long axes in a horizontal position. 1 The unit of measure-
ment is I fj,. The sizes of the spores of the Ascomycetes are those
given by Massee. 2 The sizes of the spores of the Hymenomycetes
were measured by myself and are taken from the Table in Part I.,
Chapter XIV.
Comparison of the Sizes of Spores.
Ascomycetes.
Hymenoinycete
8.
s p ecies - i i h x
5SS
Species.
Short
Axis.
Long
Axis.
Bulgaria polymorpha . 5-6
10-14
( Polyporus squamosus
Psalliota campestris
5-1
5'5
14-6
7-2
1
I Marasmius oreades
5-6
9-5
Peziza aurantia . . 7-8
15-16
$ Coprinus comatus
I Russula emetica .
7-5
7-5
12-6
8-8
Gyromitra esculenta . 9-11
17-25
Amanitopsis vaginata
10-2
10-2
fruit-body I.
Morchella gigas . . 11-14
i
21-24
Amanitopsis vaginata.
fruit-body III.
11-7
11-7
1 Cf. the end of Chap. XV., Part I. * G. Massee, British Fungiis Flora, vol. iv.
THE HELVELLACE.E
249
The Helvellaceae. The Helvellaceae are characterised by pos-
sessing long stipes which have exactly the same significance as
in the Hymenomycetes. The hyinenium becomes raised up above
surrounding leaves and herbage, so that the spores, after being
discharged from the asci, can readily be carried off by air-currents.
A specimen of one of the largest
species Morckella crassipes is
illustrated in Fig. 80. It was 9
inches high and therefore rivalled
in stature some of the largest of
the Agaricinese.
. The pileus of a Morchella is
provided with anastomosing ribs
or plates which enclose irregular
polygonal pits. The hymenium
covers the whole of the exterior of
the pileus, so that it is evident that
the plates have the same function
as the gills of a Mushroom : they
serve to increase the amount of
the spore-bearing surface. How-
ever, if one compares the pileus of
a Morchella with that of a Mush-
room, one notices that the folding
of the hymenium is vastly more
compact in the latter than in the
former. The reason for this is to
be found in the fundamental differ-
ence between basidia and asci as
spore-liberating mechanisms. The
spores of a basidium are only shot
outwards to a distance of about (H mm., whereas those of an
ascus are often propelled several centimetres. Hence adjacent
gill surfaces can be placed very near together without interfering
with the escape of the spores. On the other hand, the plates on
a Morchella pileus must be a considerable distance apart or the asci
would not have sufficient room for discharging their contents.
FIG. 80. Fruit-body of Morchella eras-
sipes, an Ascomycete which resembles
many Hymenomycetes in having its
pileus supported on a long stipe.
Photographed at Winnipeg by C. W.
Lowe. \ natural size.
2 5 o RESEARCHES ON FUNGI
It seems that, owing to their possessing basidia, the Hymeno-
mycetes are better adapted to produce large fruit-bodies which
liberate their spores into the air, than Ascomycetes. In large
fruit-bodies the hymenium of Hymenomycetes can be much
more folded than that of Ascomycetes, and therefore can produce
a much larger number of spores. It may be on this account that
the Hymenomycetes have become the dominant fungi upon the
vegetable mould of fields and forests.
CHAPTER II
THE DISPERSAL OF THE SPORES OF ASCOMYCETES BY HERBIVOR-
OUS ANIMALS ILLUSTRATED BY AN ACCOUNT OF ASCOBOLUS
IMMEItSUSPILOBO'LUS, EMPUSA MUSGJE LYCOPERDON THE
SOUND PRODUCED BY THE DISCHARGE OF SPORES, WITH
SPECIAL REFERENCE TO PILOBOLUS.
The Dispersal of the Spores of Ascomycetes by Herbivorous
Animals, illustrated by an Account of Ascobolus immersus.
Pilobolus, Empusa muscw. Ascomycetes in which the spores after
ejection from the asci are dispersed by herbivorous animals develop
on faeces and have a coprophilous mode of existence. Of these the
most striking examples are afforded by species of Ascobolus, e.g.
A. immersus, and by Saccobolus. Their spores are arranged in the
ascus more or less in two rows, and are held firmly together in
Ascobolus by their gelatinous coats (Fig. 81), and in Saccobolus by
a special investing membrane. The object, so to speak, of spore-
discharge in these fungi is to eject the spores from the ascus to as
great a distance as possible, so that they may fall at once on to the
surrounding grass. In feeding, herbivorous animals swallow the
grass and spores together. The latter pass out in the excrement
uninjured and ready to germinate. In their mode of spore-dispersal
these Ascomycetes exactly resemble Pilobolus. The attachment of
the eight spores to one another, so as to form an oval mass, prevents
the ascus jet being broken up by surface tension and thus keeps
the mass of the projectile constant. This enables the spores to be
thrown to a greater distance from the faecal substratum than would
otherwise be possible.
For the sake of comparison with the Hymenomycetes, a special
investigation was made upon the spore-discharge of Ascobolus
immersus, the asci and spores of which are of large size even for an
Ascobolus. The fungus made its appearance on a horse-dung culture
252
RESEARCHES ON FUNGI
in the laboratory. The asci were found to be heliotropic, 1 and they
were caused to point directly upwards by enclosing the culture in a
dark-chamber and reflecting light downwards upon it through a
small top window. The spores, attached together in groups of eight,
FIG. 81. Ascobolus immcrsun. a, five fruit-bodies, shown natural size, on
a section of horse dung. 6, fruit-body with five asci projecting from
the hymenium just before bursting. Two asci belonging to the next
younger series are to be seen almost hidden among the paraphyses in
the foreground, c, a young ascus and paraphyses. d and e, two fully
swollen asci isolated from the hymenium. /and g, burst asci which
have contracted to half their original length. In / the lid of the
ascus has opened as if attached by a hinge, y shows the result of an
ascus explosion watched under water with the microscope. The lid i
has been shot away along with the ascospore mass h. The eight
ascospores are attached by their gelatinous envelopes, b-i magnifi-
cation, 70.
were then discharged in a vertical direction, so that they struck and
adhered to the underside of a horizontal glass plate placed 25 cm.
above the fruit-bodies. Further experiment showed that the maxi-
mum height of projection was about 35 cm. The culture was then
set in a large glass case which was exposed to the light at a labora-
1 For the significance of heliotropism in asci, ride Chap. IV., pp. 74, 75.
DISPERSION BY ANIMALS 253
tory window. The floor of the case was covered with a sheet of
white paper. After falling upon the latter, the ejected groups of
spores could be distinguished with the naked eye as tiny dark
specks. The maximum horizontal distance to which any of them
was shot was found to be about 30 cm. In violence of spore-
discharge possibly Ascobolus immersus is not exceeded by any other
Ascomycete, although it is easily beaten by Pilobolus, which can
squirt its sporangia to a distance of more than a metre. These
performances seem truly titanic when compared with those of the
Hymenomycetes, for the maximum horizontal distance of discharge
of basidiospores was observed to be only O01-0'02 cm. 1
A group of eight Ascobolus spores clinging together was estimated
to have a volume about 2000 times greater than that of a single spore
of Amanitopsis vaginata. It is the large mass of the united asco-
spores which permits of the projectile receiving sufficient initial
velocity to carry it a distance of many centimetres. In order to-
shoot out a tiny Amanitopsis spore to an equal distance, a relatively
enormous initial velocity would require to be given to it. A parallel
case may be cited from everyday life. A good thrower can throw a
cricket ball one hundred yards. With his strongest effort, however,,
he can throw a small shot only a few feet. If he were determined
to make the shot travel as far as the cricket ball he could succeed in
doing so by putting it into a gun and driving it out with gunpowder.
The very high initial velocity which it would then receive would be
vastly greater than that imparted to the cricket ball, although the
distance traversed by both objects would be the same. It is just as
impossible for a man to throw a small shot a hundred yards as it
would be for a Mushroom to shoot out a basidiospore to a distance
of a single centimetre. In order to accomplish the latter feat, it
would be necessary for the spore to be projected with an initial
velocity of the order of 65 metres per second ! 2 On the other hand,
the united eight spores from an ascus of the Ascobolus could be shot
a centimetre with an initial velocity of only 0'2-0'3 metres per second.
1 Chap. XI., Method II.
2 Calculated by using the first equation in Chapter XVII. and taking the
terminal velocity of a Mushroom spore as 0'15 cm. per second (vide Chapter XVI.).
The spore was assumed to be spherical.
254
RESEARCHES ON FUNGI
The initial velocity which an ascospore group would need to have
imparted to it in order to fall 30 cm. from a fruit-body would be less
than 10 metres per second. 1
From the above discussion it seems that a chief factor in securing
a sufficiently large trajectory for the ascus contents of Ascobolus
immersus is the large mass of the
projectile. The projectile owes its
L size to four factors : (1) The unusually
large size of the spores, (2) the
thick gelatinous envelope round
each spore, (3) the clinging of the
c spores together, and (4) the large
mass of the discharged ascus sap.
The spores, excluding their gela-
j tinous investments, measure 35-45
x 55-65/A, and therefore are 50-100
times greater in volume than the
wind -borne spores of Peziza aur-
antia. The gigantic size of the
spores as compared with those of
the Hymenomycetes will at once be
realised by a glance at Fig. 82.
In Pilobolus, where the unopened
FIG. 82. Comparative sizes of fungus
projectiles. , spore mass of Ascobolus
*** sporangium is squirted off the spor
pestris ; c, spores of Coprinus comatus.
d, spores of Psalliota com- an <ri op hore, the projectile is rela-
All drawn to the scale given. tively of great size. That it should
be shot out farther than the contents of any ascus is, for the
mechanical reasons already discussed, not in the least surprising.
Empusa muscte, as is well known, can send its unicellular conidia
to a distance of some centimetres. Here, however, the spores
are not only very large but become coated with a thick and sticky
fluid discharged from the conidiophore. The large size of the
projectile may be at once recognised from the accompanying photo-
graph (Fig. 83).
1 Here the terminal velocity was taken to be 30-50 cm. per second (vide infra).
The spore-group was assumed to be spherical. The calculations are only very
rough approximations to actual values.
THE FALL OF ASCOSPORES 255
The large mass of a group of eight ascospores, of the sporangium
of Pilobolus, or of the conidiuin of Empusa musae, is unfavourable
to the dispersion of these structures by the wind owing to the fact
that it causes them to fall with comparative rapidity. Let us
compare the terminal vertical velocity of an Ascobolus immersus
ascospore group with that of a basidiospore of Amanitopsis
FIG. 83. Empusa rnuscse. The house-fly has been killed by the fungus and
is now fixed by its proboscis to a window-pane. The halo around the fly's
body consists of discharged conidia, many of which have been shot to a
distance of 2 cm. and some to about 3 cm. Photographed by C. W. Lowe.
| natural size.
vaginata. Assuming Stokes' Law and equal densities for the
falling particles, it may be shown that
where V =the terminal vertical velocity of the basidiospore,
Vj = the terminal vertical velocity of the ascospore group,
a = the radius of the basidiospore,
aj =the radius of a sphere with a volume equal to that of the ascospore
group.
Since, from measurements made, we may take V = 0'5 cm. per
second, a = 0'0005 cm., and ^ = 0-005 cm., we may calculate that
256 RESEARCHES ON FUNGI
Vj = 50 cm. per second. Since V is only 0*5 cm. per second, the
conclusion may be drawn that the ascospore group falls about one
hundred times more rapidly than the basidiospore. Since for
high velocities Stokes' Law breaks down and the resistance of
the air becomes proportional to a higher power of the velocity,
the rate of fall of the ascospore group is in reality somewhat
less than 50 cm. per second. Its actual value, however, must
still be enormous compared with that for the velocity of fall of a
basidiospore. The latter was observed to be only about 0-5 cm.
per second.
Since the terminal vertical velocity of an ascospore group of the
Ascobolus has been calculated to be of the order of 50 cm. per
second, we can easily understand why it is that a thick spore-deposit
often collects within a short radius of the fruit-bodies. Ordinary
convection currents, such as occur in dwelling-rooms, or slight
movements of the air in the open, can be of little use in scattering
the ejected ascus contents, although dispersion may be effected by
winds of moderate strength. On the other hand, basidiospores,
owing to their tiny size, fall very much more slowly than the
ascospore groups, and in consequence are splendidly adapted for
transport through the air. Even very slight convection currents,
such as occur almost universally near the earth's surface, are able
to carry them about and render the position where they come to
settle a matter of the greatest uncertainty.
The fruit-bodies of Ascobolus immersvus exhibit a number of
special adaptations to a coprophilous mode of existence which
enable them to liberate their spores from the sides of horse-dung
balls, &c., with success. These adaptations may be summarised as
follows : (1) The protrusion of the ripe asci, just before discharge,
to some distance beyond the surface of the hymenium; (2) the
diurnal periodicity in the ripening and discharge of successive series
of asci ; (3) the heliotropic reaction of the asci whilst becoming
protuberant; and (4) the great violence of spore-discharge. The
protrusion of the ripe asci far beyond the hymenial surface permits
of the asci making positive heliotropic curvatures. Such reactions
to light would be impossible if the asci were entirely embedded
in the hymenium like those of Pezizae. The periodicity in the
ADAPTATIONS IN ASCOBOLUS 257
ripening of the asci is of such a kind that each morning a few
asci go through their final phases of stretching and discharge their
spores almost simultaneously about midday or in the early after-
noon. After one series of asci has exploded, another immediately
begins to develop which will discharge its spores on the following
day. Owing to this periodic development of successive series of
asci, the asci always come to maturity in daylight, i.e. they always
go through their final stretching at a time when their direction
of growth can be controlled by heliotropic stimuli. The positive
heliotropism of the asci causes these structures the fungus guns
to become directed toward well-lighted positions and therefore in
general toward open spaces. When the spore-masses are shot
outwards, they thus come to have a good chance of avoiding
obstacles in their flight through the air. The orientation of the
asci must prevent a very large number of spores from being wasted
by being hot against adjacent dung balls, &c. We thus see that
the protrusion of the ripe asci, their periodic development, and
their heliotropism are intimately correlated with one another. The
great violence of spore-discharge is associated with the unusually
large size of the asci and of the spores. The clinging of the spores
together during discharge and the large mass of the projectile, as
we have already seen, are significant in that they enable the spores
to be shot to a greater distance from the horse-dung balls than
would otherwise be possible. The ascospores are thrown to such
a distance that they fall on the surrounding herbage, where they
can be devoured by herbivorous animals and thus find their way
into faeces.
Lycoperdon. In Gastromycetes the modes of spore-dispersion
are of various kinds. Sphxrobolus steilatus has a wonderful
catapult mechanism for casting a sac containing spores a dis-
tance of several inches. In the Phalloidei, 1 the fruit-bodies
are specialised for attracting flies by means of form, colour,
scent, and sweet juices. In the Tuberaceaa, the hypogean
Truffles, &c., are eagerly sought for by certain quadrupeds and
other animals. The main facts in these instances are now
well known and recognised. However, a few remarks may be
1 T. W. Fulton, loc. dt.
R
258 RESEARCHES ON FUNGI
added on Puff-balls. In the genus Lycoperdon, 1 the fruit-bodies
develop an enormous number of spores, and at maturity con-
stitute sacs full of a dry powder mixed with capillitium
threads. The peridium breaks away above so that each Puff-
ball conies to have a more or less circular opening at the
top. The arrangement is such that the spores leave a fruit-body
only when the wind is blowing at a favourable speed for their
dispersion. When the air is quiet, the spores lie safe and motion-
less within the protecting peridium. As soon, however, as the
wind becomes violent, it sweeps in gusts into the Puff-ball from
above, gradually disengages the spores from the capillitium
threads, and bears them forth to long distances. A more
effective mode of spore -dispersion can scarcely be imagined.
In connection with Puff-ball spores an interesting physical prob-
lem awaits solution. We are still ignorant why it is that the
spores of Hymenomycetes never form a mass of loose dust,
whereas this regularly occurs with those of a Lycoperdon. The
adhesiveness or non-adhesiveness of spore cell-walls must be
recognised as a matter of importance in connection with spore-
dispersion.
The Sound produced by the Discharge of Spores, with
Special Reference to Pilobolus. Although many Agarics which
have come under my notice shed spores at the rate of about
a million a minute, I have never been able to detect the least
sound caused by spore-discharge. So far as unaided human ears
are concerned, it seems likely that spore-emission by Hymenomy-
cetes must for ever be a quite silent process. On the other hand,
the discharge of spores by certain Ascomycetes appears to be
distinctly audible. Thus de Bary was able to hear "a very per-
ceptible hissing sound produced by strong specimens of Peziza
acetabulum and Helvetia cr-ispa." 2
Pilobolus, as is well known, exceeds all Ascomycetes in the
violence with which it ejects its projectiles. Coemans records
that the sporangia can be projected to a height of over
1 Vide Chap. V. p. 86.
2 De Bary, Comparative Morphology and Physiology of the Fungi, etc., English
translation, 1887, p. 92.
SOUNDS PRODUCED BY PILOBOLUS 259
3 feet, 1 and Grove found that on one occasion the maximum hori-
zontal distance of discharge was 4 feet 10 inches. 2 The largest of all
the Piloboli is P. loiigipes, the stipe of which is usually 2-3 cm.
long, whilst the diameters of the sporangium and subsporangial
swelling are 0-5 mm. and 1 mm. respectively. When I placed
the sporangiophores of this species so that they inclined obliquely
upwards at an angle of about 45, several sporangia were shot
more than 5 feet in a horizontal direction, and one to a distance
of 6 feet 2 inches. Grove noticed that, when a sporangium strikes
one in the face, one can distinctly feel the blow, like that of a
small drop of rain, 3 and he called attention to the fact that each
discharge is accompanied " by a faint but distinctly audible ' puff,'
like the sound of a minute pop-gun." 4 From personal experience
with a number of Pilobolus cultures, I am able to confirm Grove's
statements both as to feeling the blows of the sporangia and also
as to hearing the sound of the explosions. Some horse-dung
cultures of Pilobolus Kleinii were carefully watched during the
mid-day hours on several successive days. At first I mistook very
slight sounds produced involuntarily from my collar and mouth for
sounds proceeding from the fungus. However, when these sources
of error had been eliminated, I found that it was still possible to
detect some, although perhaps not all, of the discharges. On
listening very intently in a quiet room, two sounds were to be
heard : firstly, a little click as a sporangium left its sporangio-
phore, and secondly, a more metallic sound, whenever a sporangium
struck the glass side of the crystallising dish which contained
the culture. So far as I am aware, the sound of the projectiles,
made on striking obstacles, has not hitherto been noticed. Its
audibility can be very much increased by a method devised by
Mr. F. Wakefield, who was assisting me in the laboratory. One
makes use of a drum consisting of a glass funnel, 3 or 4 inches
in diameter, across the mouth of which a sheet of thin tissue
1 Coemans, Monographic du Genre Pilobolus, 1860, p. 39 ; quoted from Grove's
monograph, p. 15.
2 W. B. prove, Monograph of the Pilobolidse, Birmingham ; reprinted from the
Midland Naturalist, 1884, vol. vii. p. 219.
3 Loc. cit., p. 16. 4 Loc. tit., p. 15.
26o RESEARCHES ON FUNGI
paper has been pasted. If one holds such a drum a little way
above the Pilobolus culture, one can readily hear the bang each
time a sporangium hits the tissue paper. I found that Mr.
Wakefield could detect the sound made on the drum at a distance
of 21 feet.
GENERAL SUMMARY
The following is a summary of the more important results obtained
during the investigations
PART I
CHAPTER I. The spores of the Hymenomycetes are very adhesive when
freshly liberated. In consequence of this, special arrangements are neces-
sary for their liberation from the surfaces of gills and hymenial tubes, &c.
Successful liberation can take place only when the hymenium is so situated
that it occupies a vertical position or looks downwards at a greater or less
angle.
Paraphyses are useful as spacial agents. They prevent the adhesive
spores of adjacent basidia from coming into contact during development
and discharge. The functions of cystidia are for the most part still quite
unknown.
Occasionally certain species of Coprinus give rise to fruit-bodies which
are normal in size and form, but are either partially or completely sterile.
The basidia fail to produce spores. Fruit-body sterility of this kind was
observed in Coprinus fimetarius, var. cinereus, and also in an ephemeral,
coprophilous species, which has been called C. plicatiloides.
Fruit-bodies are frequently visited by Springtails (Collembola), Mites
(Arachnida), and Fungus Gnats (Mycetophilidse). Their relations with
these animals stand in need of a detailed investigation.
Direct sunlight injuriously affects the vitality of the dry spores of
Schizophyllum commune and of Dsedalea unicolor. Possibly the colouring
matters deposited in the walls of the spores of Coprini and of other
Hymenomycetes may serve a useful purpose by screening off certain of
the sun's rays from the living protoplasm.
CHAPTER II. The disposal of the hymenium beneath a fruit-body on
gills, on spines, or in tubes, &c., instead of on a flat surface, is an economi-
cal arrangement which permits of a great increase in the number of spores
which a fruit-body of a given size may produce. Species of the genus
Fomes appear to be the most highly specialised in this respect. The
specific increase in the extent of the hymenium due to the presence of
gills and tubes was measured in a few cases. In the Mushroom it was
262 RESEARCHES ON FUNGI
found to be 20; in Fomes vegetus 148 for one year, and 500 for three;
whilst in a large and old specimen of Fomes igniariun it proved to be
nearly 1000.
The crowding of the gills and the reduction in diameter of the tubes in
certain fruit-bodies (e.y. those of the Mushroom and of Fomes igniariuft),
after allowing for a small margin of safety, appear to have reached their
limits consistent with the violent horizontal discharge of the spores from
the basidia.
CHAPTER III. The fruit-bodies of most species of Hymenomycetes are
very rigid. This rigidity is of considerable importance in keeping the
axes of the tubes of Polyporese, the planes of the gills of Agaricinese, &c.,
in vertical positions. Slight swaying movements cause loss of spores. In
a Mushroom it was calculated that, when two adjacent gills are tilted from
their vertical planes to an angle greater than the critical angle of about
2 30', some of the spores are unable to escape from the interlamellar
spaces. With a tilt of about 5, half the spores are lost ; and with a tilt
of about 9 30', four-fifths of them. The rigidity of stipes in many species
is secured by hollow cylindrical form and by unequal tensions in the layers
of cells.
CHAPTER IV. The growth movements of a fruit-body can be regarded
as so many adjustments of a delicate machine made with the object of
placing the hymenium in the best possible position for liberating the spores.
A Mushroom and the ephemeral, coprophilous Coprini exhibit four such
adjustments, and Polyporus squamosus five. The nature of the adjustments
is correlated with the general structure of the fruit- bodies and with the
orientation of the substratum.
The amount of eccentricity of the pileus of Polypoi-us sguamosus is con-
trolled by a morphogenic stimulus of gravity.
The stipes of certain ephemeral Coprini, just before the pilei expand,
are extremely sensitive to the stimulus of gravity. When a stipe had been
changed from the vertical to the horizontal position, a distinct upward
curvature was noticed after a stimulation of T5 minutes. Another stipe,
similarly displaced, gave a distinct macroscopic reaction to the stimulus of
gravity after 3 minutes' stimulation, and turned through a complete right
angle, so as to regain a vertical position, in 17*5 minutes. The last 80
were turned through with a greater angular velocity than that of the
minute-hand of a clock. This angular velocity is far greater than that
known for any Phanerogam, or indeed any other plant organ when stimu-
lated by gravity.
CHAPTER V. In perfectly still air, the spores liberated from a pileus
placed above a horizontal sheet of paper fall vertically downwards and
GENERAL SUMMARY 263
produce a spore print consisting of radiating lines corresponding to the
inter-lamellar spaces. Extremely minute convection currents give a hori-
zontal drift to the falling spores and cause the spore-deposit to become
cloudy.
The number of spores liberated by large fruit-bodies amounts to thou-
sands of millions. A specimen of Psalliota campestris with a diameter of
8 cm. was found to produce 1,800,000,000 spores, one of Coprinus comatus
5,000,000,000, and one of Polyporus squamosus 11,000,000,000. The rate
of elimination of the spores or young plants by death can be shown to be
enormous. The most prolific kind of fish is not so prolific as a Mushroom
plant. It was estimated that a large fruit-body (40 x 28 x 20 cm.) of Lyco-
perdon bovista, Linn., the Giant Puff-ball, contained 7,000,000,000,000
spores, or as many as would be liberated by 4000 Mushrooms, each having
a diameter of 8 cm.
CHAPTER VI. With the unaided eyes by daylight, clouds of spores
were observed to be given off continuously for thirteen days from the
underside of a large fruit-body of Polyporus squamosus. It was found that
each hymenial tube was liberating spores from every part of its hymenium.
The visible discharge of spores appeared to be unaffected by light conditions
or by changes in the hygroscopic state of the atmosphere. The formation
of irregular clouds, wreaths, and curls of spores is not due to intermittent
spore- emission, but is brought about by air-currents sweeping beneath the
fruit-body.
CHAPTER VII. Spores falling from any fruit-body suspended in a suit-
able glass chamber, e.g. a closed beaker, can be seen in clouds or individually
without magnification by using a concentrated beam of light. Much use
was made of this discovery in the research.
The beam-of-light method can be used to make a very simple and
effective laboratory demonstration of the discharge of spores from Mush-
rooms, itc. It may be carried out with great convenience at any time by
using as material the mature xerophytic fruit-bodies of Lenzites betulina,
Schizophyllum commune, Polystidus versicolor, &c. These can be kept dry
in bottles for months or years. After wet cotton-wool has been placed
above them they quickly revive, and they begin to shed their spores within
six hours. The emission of the spores continues for days.
CHAPTER VIII. Spore-discharge from any fruit-body under normal
conditions is continuous. The period of spore-discharge in some species
lasts for a few hours, in others days, and in yet others for weeks. With
the beam-of-light method a fruit-body of Schizophyllum commune and also
one of Polystictus versicolor were both observed to shed a continuous stream
of spores for sixteen days. A specimen of Lenzites betulina shed spores for
264 RESEARCHES ON FUNGI
ten days. These fruit-bodies, doubtless, had already shed spores for some
time before they were gathered.
After the number of spores produced had been estimated and the length
of the spore-fall period had been observed, it was calculated that large
fruit-bodies of Psalliota campestris, Coprinus comatus, Polyporus squamosus,
<fcc., shed about a million spores a minute for two or more days.
CHAPTER IX. The fruit-bodies of corky or leathery consistency growing
on sticks and logs are xerophytic. They can be dried up without any loss
of vitality. On access to moisture they revive in a few hours and resume
the function of discharging spores. The retention of vitality after desicca-
tion in some species is continued for years. The spores liberated from
revived fruit-bodies are capable of germination. Typical genera consti-
tuting a xerophytic hymenomycetous log-flora are : Lenzites, Polystictus,
Stereum, &c.
The fruit-bodies of Schizophyllum commune possess special adaptations
for a xerophytic mode of existence. The gills are partially or completely
divided down their median planes into two vertical plates. Whilst desicca-
tion is proceeding, the two plates of each of the longer and deeper gills
bend apart and spread themselves over the shorter and shallower gills.
When desiccation is complete, the whole of the hymenium is hidden from
external view and the fruit-body is covered both above and below with a
layer of hairs. The closing up of the fruit-bodies at the beginning of a
period of drought serves to protect the hymenium from external enemies.
A fruit-body can retain its vitality in the dried and closed-up condition for
two or more years. When allowed to absorb free water through the top
of the pileus, it revives in a few hours. The two plates of each pair return
to their original vertical positions, and again become closely apposed. The
liberation of spores is then recommenced, and may last for some days.
CHAPTER X. The fruit-body in some species can only be developed so
as to produce a pileus when subjected to the morphogenic stimulus of light.
When a hymenium has once been produced it sheds its spores indepen-
dently of light conditions and of the direction of gravitational attraction.
So long as a fruit-body itself contains sufficient water, spore-discharge
appears to continue without being affected by the hygroscopic state of the
atmosphere.
Some of the xerophytic fruit-bodies growing on logs, &c., continue to
shed their spores at the freezing-point of water. The range of temperature
permitting spore-discharge in the case of Lenzites betulina was found to be
approximately 0-30 C.
When a fruit-body is placed in hydrogen or carbon dioxide, the libera-
tion of spores quickly ceases. The presence of oxygen in the surrounding
atmosphere appears to be essential for the continuance of spore-discharge.
GENERAL SUMMARY 265
In pure oxygen fruit-bodies shed their spores for several hours at the same
rate as in air.
When a fruit-body is subjected to the vapour of ether or chloroform,
spore-discharge ceases almost instantaneously, but can be resumed when
the anaesthetic has been removed. A fruit-body of Lenzites betulina re-
covered its spore-liberating function after this had been inhibited by ether
vapour for a week.
CHAPTER XI. The four spores on each basidium are discharged suc-
cessively. They leave the sterigmata within a few seconds or minutes of
one another.
Each spore is shot out violently from its sterigma to a distance of about
CHAPTER XII. The propelling force during spore-discharge seems to
be provided by the pressure of the cell-sap of the basidium upon the cell-
wall, and possibly by a similar pressure in the spore. On the discharge
of a spore, the sterigma breaks across but does not open. Spore-discharge
in the Hymenomycetes appears to resemble that in Empusa Grylli, and
may be said to be brought about by a jerking process, which may be con-
trasted with the squirting process of Empusa mnscas and the Ascomycetes.
CHAPTER XIII. The specific gravity of spores can be determined
approximately by using heavy fluids contained in a counting apparatus,
the chamber of which is O'l mm. deep. The specific gravity of spores of
Amanitopsis vaginata was found to be nearly that of water, namely, 1-02,
whilst that of the much heavier Coprinus plicatilis spores proved to be
approximately 1-21.
CHAPTER XIV. The size of spores can be measured with accuracy and
rapidity by using a Poynting Plate Micrometer. The apparatus has been
described.
The average size of the spores of a fruit-body may differ considerably in
different fruit-bodies of the same species. This fact may well account for
the want of agreement of spore measurements as given by different
mycologists.
CHAPTER XV. The rate of fall of spores in still air was determined for
the first time. A small piece of a fruit-body was placed in a vertically-
disposed compressor cell. The falling spores were observed with a hori-
zontal microscope and their rate of fall accurately recorded upon a revolving
drum.
The first direct test of the applicability of Stokes' Law to the fall of
microscopic spheres in air has been carried out by determining the size,
266 RESEARCHES ON FUNGI
specific gravity, and terminal velocity of the spherical spores of AnttBtitoptu
vafjinata. The rate of fall of the spores was found to be about 46 per cent,
greater than was expected. While, therefore, the observed speed has proved
to be of the same order of magnitude as the calculated, Stokes' Law has not
been confirmed in detail. No fully satisfactory reason for the discrepancy
between theory and observation has so far been found.
CHAPTERS XV. AND XVI. The rate of fall of hymenomycetous spores
ranges from 0'3 to 6'0 mm. per second. It varies with the size of the
spores, their specific gravity, and the progress of desiccation. The rela-
tively very small spores of Collybia dryophila in very dry air was found to
fall at an average rate of 0*37 mm. per second, whilst the relatively very
large spores of Amanitopsis vaginata in a saturated chamber attained a
speed of 6'08 mm. per second. The spores of the Mushroom (Psalliota
campestris), shortly after they have left the pileus, fall at a speed of
approximately 1 mm. per second.
CHAPTER XVI. The spores fall most rapidly between gills, down tubes,
&c., immediately after liberation from the sterigmata. After emerging
from the fruit-bodies, they dry up within about one minute. The diminu-
tion of volume causes a considerable reduction in the rate of fall.
CHAPTER XVII. The importance of violent spore-discharge lies in the
fact that thereby the very adhesive spores are prevented from touching one
another or any part of the hymenium whilst escaping from the fruit-body.
Each spore is shot out more or less horizontally into the spaces between
the gills, in hymenial tubes, &c. The horizontal motion is very rapidly
brought to an end owing to the resistance of the air. In consequence of
this, and also of the attraction of gravitation, the spore describes a sharp
curve and then falls vertically downwards.
The path of the spore between the gills, in tubes, &c., has been called
the sporabola, and is remarkable in that it appears to make a sudden bend
approximately through a right angle. When for any spore the terminal
vertical velocity and the maximum horizontal distance of discharge have
been determined, its sporabola becomes amenable to a satisfactory mathe-
matical treatment. It was observed that the spores of Amanitopsis vaginata
are shot outwards from the gills in a horizontal direction to a maximal
distance of 0'2 mm. It was calculated that they complete this movement
in approximately ^^ second, and leave the sterigmata with an initial
horizontal velocity of approximately 40 cm. per second. The steady, ter-
minal, vertical velocity of about 0'5 cm. per second is attained by the time
a spore has fallen a distance equal to its own diameter, i.e. about 10 [j..
CHAPTER XVIII. At the moment of discharge, or within a few seconds
GENERAL SUMMARY 267
afterwards, the majority of spores of the Mushroom, (fee., become electrically
charged. The charges are relatively of different strengths, and either
positive or negative. A few spores appear to be unelectrified. No bio-
logical significance has been ascribed to these facts.
CHAPTER XIX. In the Agaricineae there are two distinct spore-produc-
ing and spore-liberating types of fruit-body the Coprinus comatus type and
the Mushroom type. These differ from one another in several structural
and developmental details.
In the Coprini " deliquescence " is a process of autodigestion which
renders important mechanical assistance in the process of spore-discharge.
Jt was more especially studied in the case of Coprinus comatus. The spores
on each gill ripen and 'are discharged in succession from below upwards.
Autodigestion leads to the removal of those parts of the gills which have
already shed their spores and thus permits of the continued opening out of
the pileus. By this means the necessary spaces for the violent discharge
of the spores from the basidia are provided. The spores, after describing
sporabolas, fall vertically downwards between the gills. On emerging from
the pileus they are scattered by the winds. " Deliquescence " is in no way
connected with the visits of insects to the fruit-bodies.
The genus Coprinus may be regarded as a specialised offshoot from
a more generalised fungus of the Mushroom type. There appears to be
no satisfactory evidence in support of Massee's view that " in the genus
Coprinus we have in reality the remnant of a primitive group from which
have descended the entire group of Agaricinese."
CHAPTER XX. One of the chief functions of the stipe is to provide
a space usually one or more inches high between the under surface of the
pileus and the substratum on which the fruit-body may grow. Owing to
the very small rate of fall of the spores and the relatively very much
greater average horizontal speed of air-currents near the ground, the
space is amply sufficient under normal conditions to permit of the falling
spores being carried away from the fruit-body and deposited at a distance
from it.
Falck's theory, that the heat produced in pilei by respiration and in
consequence of the presence of maggots is of importance in creating con-
vection currents which scatter the spores, has been discussed. If partially
true, it is of limited application, and further investigations are necessary
in order to decide its value.
CHAPTER XXI. Coprophilous Hymenomycetes have fruit-bodies
adapted to their peculiar habitat both in form and in reactions to external
stimuli.
268 RESEARCHES ON FUNGI
Slugs are probably of but minor importance in dispersing the spores of
Hymenomycetes.
Slugs do not find the fruit-bodies of all Agaricin* equally palatable,
but prefer to starve rather than eat those of certain species.
PART II
CHAPTER I. The spores of some Discomycetes (Peziza, Bulgaria,
Gyromitra, &c.) are scattered by the wind, whilst others (Ascobolus immersus,
Saccobolus, &c.) are dispersed by herbivorous animals. Each mode of
spore-dispersion is correlated with special adaptations in the asci.
The spores of Peziza repanda are shot up into the air to a height of
2-3 cm. The eight spores from an ascus separate from one another almost
immediately after leaving the ascus mouth, and are then carried off by the
wind. The fact that the ascus jet breaks up on leaving the ascus was
observed by means of the beam-of-light method.
Puffing is probably not due (as de Bary supposed) to the mere with-
drawal of water from asci. Solutions of grape sugar, glycerine, sodium
chloride, and potassium nitrate, which merely withdraw water from the
ripe asci of Peziza rrpanda, do not cause their explosion. On the other
hand, solutions of many poisonous substances, e.g. iodine, mercuric chloride,
silver nitrate, copper sulphate, sulphuric acid, acetic acid, and alcohol, give
rise to marked puffing. Two alkalies sodium hydrate and sodium car-
bonate kill the asci without causing them to discharge their contents.
It seems probable that puffing is caused by a stimulus given to the proto-
plasm in contact with the ascus lid.
The physics of the ascus jet in Peziza repanda has been discussed. It
seems probable that the separation of the eight spores of an ascus during
their upward flight into the air is due to considerable differences in the
initial velocities given to the individual spores upon their discharge.
Surface tension probably plays but a minor part in breaking up the ascus
jet. When the ascus is regarded as an apparatus for squirting out a jet
in such a manner that the jet immediately breaks up into eight parts so
that each part contains a spore, its structure becomes more intelligible.
The eight spores in an ascus of Peziza repanda are loosely attached
together, and the row of spores is anchored to the ascus lid by a special
protoplasmic bridle. De Bary's hypothesis of currents is unnecessary in
accounting for the means by which the spores are caused to take up their
characteristic positions in the ascus.
The wind-borne spores of Ascomycetes and of Hymenomycetes are
of the same order of magnitude with respect to their short diameters,
and are therefore equally well adapted to be dispersed by ordinary air
movements.
GENERAL SUMMARY 269
The Hymenomycetes, owing to the possession of basidia, are better
organised for the production of large fruit-bodies which discharge their
spores into the air than Ascomycetes. This is due to the fact that,
without interfering with the escape of the spores, a hymenium contain-
ing basidia can be more compactly folded than one containing asci.
The present dominance of large-fruited Hymenomycetes over large-
fruited Ascomycetes in forests and fields may be indirectly due to the
fundamental difference between basidia and asci as spore-discharging
mechanisms.
CHAPTER II. Ascobolus immersus is specially adapted to a coprophilous
^mode of existence. The special adaptations of its fruit-bodies are : (1) The
protrusion of the ripe -asci beyond the general surface of the hymenium,
(2) the diurnal periodicity in the ripening of successive groups of asci,
(3) the positive heliotropism of the asci, (4) the considerable distance to
which the spores are ejected (sometimes 30 cm.) with which is associated
(5) the large size of the asci and spores, and (6) the clinging of the eight
spores together whilst describing their trajectory through the air. The
adaptations are such as to permit of the asci discharging their contents
so that these may be shot outwards clear of immediate obstacles, such
as dung balls, fec., and fall on the surrounding grass where they may be
swallowed by herbivorous animals.
The projectiles of Ascobolus immersus, Empusa, and Pilobolus are much
larger than those of the Hymenomycetes. The distance to which they are
ejected is proportional to their size.
The clinging together of the eight spores in the ascus of Ascobolus
immersus involves an increase in the mass of the projectile, and thereby
enables the spores to be shot to a greater distance than that to which they
would be shot if they separated from one another immediately after leaving
the ascus mouth.
When sporangiophores of Pilobolus longipes are inclined upwards at an
angle of about 45, the sporangia are often thrown to a horizontal distance
of 5 feet. The maximum horizontal distance of ejection observed was
6 feet 2 inches.
Grove's observation that the sound of the discharge of the sporangia
from the sporangiophores is audible, has been confirmed. Another sound
can be detected when the sporangia strike against a glass vessel or a piece
of paper. The impingement of sporangia upon a tissue paper drum could
be distinctly heard at a distance of 21 feet.
Attempts to detect a sound proceeding from fruit-bodies of the Mush-
room and Polyporus squamosus, when discharging about a million spores
a minute, failed. Probably for unaided human ears, the liberation of the
spores of Hymenomycetes will for ever remain a quite silent process.
EXPLANATION OF PLATES l.-V
PLATE I
FIG. 1 Coprinus comatus. Vertical section through a large fruit-body showing
the thin flesh, the vertically-placed gills, darkening from below upwards, and the
hollow stipe, m, marginal band covered with cystidia. Natural size.
FIG. 2. Psalliota campestris. Section through a ripe fruit-body at maturity to
be contrasted with that of Coprinus comatus in Fig. 1. Its flesh is thick, and the
gills are nearly horizontally outstretched. Specimen obtained from a field.
Natural size.
FJG. 3. Section through the hymenium of Polyporus squamosus, constructed
from sketches made with a camera lucida. , a basidium with unripe spores ; b,
a basidium with ripe spores ; c, a basidium with two of its spores already dis-
charged ; d, a basidium which has discharged all four spores. Paraphyses separate
the basidia. Magnification, 625.
FIG. 4. Psalliota campestris. Vertical and transverse section through three
gills. The hymenial surfaces are almost vertical. The arrows indicate the spora-
bolas or paths described by spores after violent discharge from the sterigmata.
Each spore is shot outwards horizontally to a distance of (H-0'2 mm., and after
making a sharp turn falls vertically downwards in the space between the gills.
Magnification, 25.
FIG. 5. Coprinus comatus. Transverse section through some of the gills
whilst the spores are ripening, s, s, spaces between the gills lined by the
hymenium ; e, inner swollen edges of gills covered with cystidia ; /, pileus flesh.
Magnification, 8.
PLATE II
Figs, all of Coprinus comatus.
FlG. 6. Vertical section through a young fruit-body shortly after it had
appeared above the ground, s, level of soil. Natural size.
FIG. 7. Vertical section through an older fruit-body shortly before the gills
separate from the stipe, s, level of soil. Natural size.
FIG. 8. Vertical section through a fruit-body after autodigestion has begun.
The gills are becoming liquefied from below upwards. The dotted lines show the
shape and position of the gills at the moment autodigestion began, s, lower
edge of gill where spore-discharge and subsequently autodigestion first become
active ; , oblique edge of gill where spore-discharge and autodigestion are taking
place ; m, marginal band on gill edge covered with cystidia. Natural size.
FIG. 9. Vertical section through a fruit-body which has become helmet-
shaped. By autodigestion the gills have now become reduced to about one-third
their original length. , edge of gill where spore-liberation and autodigestion
270
EXPLANATION OF PLATES 271
are still in progress, m, marginal band on gill edge covered with cystidia.
Natural size.
FIG. 10. Vertical section through a fruit-body when autodigestion is nearly
completed. The remains of the gills have now become horizontally outstretched.
Liquid drops may be seen at d in such a position that they do not interfere with
the liberation of the spores into the air. a, edge of gill where spore-liberation
and autodigestion are still in progress, m, marginal band on gill edge covered
with cystidia. Natural size.
FIG. 11. Fruit-body in the last stage when spore-liberation has ceased. The
gills have now entirely disappeared. The central part of the pileus flesh still
crowns the stipe. Natural size.
FIG. 12. Semi-diagrammatic drawing of part of a gill surface m the region of
autodigestion. There are five zones running parallel to the oblique gill edges :
(1) a-af, zone of basidiawith ripe spores. (2) b-b', zone of basidia discharging spores
into an interlamellar space. The spores are shot off their sterigmata successively,
so that in this zone some basidia have three spores left upon them, some two, and
some one, whilst some have lost them all. (3) c-c', zone of basidia which have dis-
charged all their spores. (4) d-d', zone of autodigestion. The basidia and para-
physes are becoming indistinct and gradually liquefied. (5) e-e', the dark liquid
film on the gill edge containing the products of autodigestion. Magnification,
320.
PLATE III
Figs. 13-17 all of C'oprinus comatus.
FIG. 13. Surface view of part of one side of the inner swollen edge of a gill
before autodigestion has begun, m, marginal band covered with cystidia, c ;
h, hymenium containing basidia with ripe spores. Magnification, 1 20.
FIG. 14. Transverse section through the inner swollen edges of three gills
before autodigestion has begun. The swollen edges contain large air-spaces, a a,
and are covered by cystidia, c. The spaces s s between the gills are lined by the
hymenium. The basidia each bear four spores; but of these, for the sake of
clearness, two only are shown. Magnification, 120.
FIG. 15. Surface view of a piece of gill, O'Ol mm. by 0*02 mm., in
the region of ripe spores close to the zone of spore-discharge. Each basidium
bears four black spores, and is separated from its neighbours by paraphyses.
Magnification, 320.
FIG. 16. Section through the hymenium in the region of spore-discharge.
The two uppermost basidia each bear four ripe spores ; the middle basidium has
discharged two spores, the next below that three spores, and the lowest basidium
of all four spores. Two sporabolic paths, one with the horizontal distance O'l mm.
long and the other with it 0'15 mm. long, are also shown. Magnification, 320.
FIG. 17. Diagram showing the paths of spores during discharge from the gills.
A, transverse section cut horizontally through three gills. The dark, free edges
are covered by liquid films produced by autodigestion. The arrows show the
direction in which the spores are discharged from the zones of spore-discharge,
and also the distance to which they travel horizontally. B shows a piece of one
of the gills seen from the side. The arrows indicate by their positions and direc-
tions the vertical paths of the spores after leaving the zone of spore-discharge.
272 RESEARCHES ON FUNGI
C shows the appearance of the three gills when looked at edgewise from the stipe.
The arrows indicate the sporabolas or paths taken by the spores when escaping
from the gills.
Figs. 18-20 all of Coprinus micaceus.
FIG. 18. Young fruit-body from which spore-liberation has begun. Natural
size.
FIG. 19. Vertical section through a young fruit-body before spore-liberation
has begun. The gills are turning brown and ripening their spores from below
upwards. Natural size.
FIG. 20. a, ft, c, and d. Successive stages during the autodigestion of the
gills. Drawn from four different fruit-bodies. Natural size.
PLATE IV
Figs. 21-24 all of Coprinus comatus.
FIG. 21. Characteristic group of fruit-bodies growing in a field. Owing to
excessive crowding, parts of the free margin of the pileus of two individuals have
stuck to younger fruit-bodies. Magnification about 6.
FIG. 22. Specimens placed in a row and photographed to show the various
stages of development. The gradual opening out of the pileus and the curling up
of its free margin during autodigestion, and also the lengthening of the stipe,
may be traced from right to left. Magnification about 7.
FIG. 23. Underside of a fruit-body liberating spores. Autodigestion is
taking place where the gills look black and are evidently separated by free
spaces. Spores are being discharged into the air from hymenial zones just above
and parallel to the wet gill edges. The inner and higher parts of the gills, where
autodigestion is not yet taking place, are still united at their edges by the large
white cystidia. Natural size.
FIG. 24. Photograph of a helmet-shaped fruit-body in a field. A marked
feature is the outwardly folded remains of the gills at the free margin of the
pileus. A drop of " ink " hangs from the pileus opposite the stipe. The dark
liquid drop is in such a position that it does not interfere with the discharge of
the spores into the air. Magnification about ^.
FIG. 25. View of the underside of a mature pileus of Psalliota campestris
grown on a Mushroom bed. The gills are horizontally outstretched and free
from each other throughout their length. Spores are liberated from all the inter-
lamellar spaces and from every part of them simultaneously. Natural size.
FIG. 26. The Poynting Plate Micrometer and a microscope for using it. The
glass plate, p, can be pushed into the slot si. The stand, st, has a vertical arm, a,
with a scale, sc. The plate, p, is attached to the horizontal rod, r, which can be
rotated by means of the lever, I, which terminates in a small framework carrying
a piece of glass on which is etched a line parallel to the lever. For further
description see the text.
FIG. 27. Polyporus squamosus. Spore-deposit made in about twenty-four
hours from the hymenial tubes of a piece of the pileus. Each tube has produced
its own heap of spores. Natural size.
FIG. 28. Polyporus squamosus. Spore-deposit made in about twenty-four
EXPLANATION OF PLATES 273
hours from a vertical section of the pileus. Each half-tube has liberated spores
throughout the whole length of its hymenium-bearing surface. Natural size.
FIG. 29. Measurement of the rate of fall of spores. The observer is looking
through the horizontal microscope at a field focussed below the gills of a piece of
pileus contained in a vertically-placed compressor cell held in a clip. The cell is
illuminated by diffuse daylight reflected from a glass roof to the eye by means of
a mirror. On the table to the right is placed a drum driven by electricity. The
chronometer at the back is used for making time-records. The small battery on
the right of the drum is connected with the fountain pen which touches the drum
paper as the latter revolves, and also with the tapping-key upon the knob of which
the observer has his first finger. As a spore passes the three eye-piece lines in
t the field of view, the observer makes three successive taps upon the tapping-key.
The fountain pen in response makes three deviations from its normal course on
the paper. Each spore record is afterwards measured on the drum by means of a
steel tape.
FIG. 30. Amanitopsis vaginata. A fruit-body photographed in a wood.
Magnification about .
PLATE V
Figs, all of Polyporus squamosus.
FIGS. 31, 32, 33, and 34. Successive stages in the development of two fruit-
bodies grown on a log in the light. Natural size.
FIG. 31. One day old. A stromatous knob half hidden in a rift of the log has
developed four conical processes.
FIG. 32. Two days old. The four conical processes have become flattened at
their ends in preparation for the development of pilei.
FIG. 33. Three and a half days old. Two of the conical processes have
ceased to grow ; the other two have become converted into young fruit-bodies.
These have obliquely-placed stipes, and their pilei, which at first were sym-
metrically developed, already show distinct signs of eccentricity. The growth of
the stipes has raised the pilei so that their upper surfaces have now come to lie
in a horizontal plane.
FIG. 34. Nearly five days old. The eccentricity of the pilei and their growth
in a horizontal plane have become very marked. The posterior sides of the pilei
are in contact and have now ceased to develop. The stipes have attained their
maximum size.
When seven days old the fruit-bodies were fully extended and shedding spores
abundantly, although the hymenial tubes had not yet reached their maximum
length. The left-hand pileus had become 1 1 cm. wide from the posterior to the
anterior edge, and the right-hand one 9 cm. wide. When looked at from above,
both pilei appeared very eccentric and resembled the pileus shown in Fig. 4 in
the text (p. 28). The last stage is shown in Fig. 34 in the text (p. 84).
FIG. 35. Young fruit-body about three days old. It has developed from the
only conical process produced by the stromatous knob. The pileus is very
centric. Natural size.
FIG. 36. Stromatous knob giving rise to a number of conical processes in the
dark. Natural size.
S
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