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Un des symboles suivants apparaitra sur la dernidre image de cheque microfiche, selon le cas: le symbole ^^- signifie "A SUIVRE", le symbole V signifie "FIN". Maps, plates, charts, etc., may be filmed at different reduction ratios. Those too large to be entirely included in one exposure are filmed beginning in the upper left hand corner, left to right and top to bottom, as many frames as required. The following diagrams illustrate the method: Les cartes, planches, tableaux, etc., peuvent dtre filmis d des taux de reduction diff6rents. Lorsque le document est trop grand pour dtre reproduit en un seul clich6, il est film6 A partir de Tangle sup6rieur g.iuche, de gauche d droite, et de haut en bas, en prenant le nombre d'images ndcessaire. Les diagrammes suivants illustrent la mdthode. 1 2 3 1 2 3 4 5 6 ia Air 1) '-/^li' [From the Qfarterly Journal of the Grolooical Society for May 1871.] On the Structurr and Affinities of Sioillakia, Calamitrs and C'alamodendkon. By J. \V. Dawson, LL.D., F.U.S., F.G.S,, Principal of M^Oill Univeryity. (Read May 11, 1870 ».) [Plates VII -X.] 1. SiGILLAUIA. The difficulty of arriving at a coiTcct knowledge of tlie structure of those curious trees is caused principally by the unecjual durability of the different piirts of the stem. It arises from this that some portions liavc usually perished, while others were in process of mineral iz'ition, and the portions which remain have in a great degree lost their original form and arrangement. The outer bark, while extremely durable, was too impenetrable to be jjreserved in any other way than as compact coal. The fibres of the bark and of the woody axis are often mineralized or imperfectly preserved as mineral charcoal. • The cellular poiiions of the bark and of the axis have usually entirely disappeared. Still, im[)erfectly preserved stems can be obtained in great abundance in any coal-field by those who are content to work on such unpromising material. Probably the finest specimen of a t^hjillaria hitherto described is tliat of S. ehf/ans, so admirably figured by IJrongniart, and which has long served to give to the student of pala>ol)otany his ideas of the structure of the genus. Unfortunately, however, Brongniart's specimen represents a small or young stem belonging to the some- what aberrant subgenus FaruJuria ; so that it fails to give an adequate idi'a of the structure of the typical fossil Sii/Ulariir, which aro much more common and important, at least in the coal-fields of Nova Scotia. The structure of these last, as observed in specimens obtained at the South Joggins, was, I believe, first descrilied by mo in my paper on the Vegetable Structures in Coal, published in the 'Journal' of this Society in 1855K The specimens subsequently figured in the ' Journal ' of this Society, and in the ' Transactions ' of the lloyal Society, by Mr, Binney, under the name of /S, vascida7-is, belong, in ])art at least, to types of structure (]uite distinct from that of the ti'ue Sl(/dlaninf. My own results as to the typical Sn/iUariff are thus shortly summed up in my ])aper on the " Conditions of DcjKtsition of Coal" J : — "In the restricted genus Siijilhtriu the ribs are stmngly developed, except at the base of the stem ; they are usually nnich * For the discussion on this paper see Quart, Journ, Gaol. Soc. vol. xxvi. p. 4'.)(). t It would seem that the speciniens figured by Mr. Binnoy us SicjiUuria vascularis (Philos. Traiis. vol. civ.) belong in part to the axia of a remarkable Sigillarioid tree, of which specimens have been kindly shown to nu; hy Prof, Williamson, and in part (especially pi. xxxv. fig.-'. .^ & (i) to the vholc .stnn of a Lej>i(/o(fn/c/ro7i. The latter plant has been desi'ribed hy Mr. C'arruthers (i.s L('pit(oihndro)i srl/if/inniflfs. J Qnnrt. Journ. (ieul. >;oi'. vol. xxii. ]>. l'-".'. 148 PROCEEDINOS Olf THE OEOLOOICAL SOCIKTY. broader than the oval or elliptical tripunctato areolcs, and are striated lon"itudinally. The woody axis has both discigorous and scalaritbrni tissues, arranged in wedges, with medullary rays as in oxogens ; the pith is transversely partitioned in the manner of Sternhenfm ; and the inner bark contains great (piantities of long and a{)partuitly very diirahle fibres, which I have, in my descriptions of the structures in the coal, named ' bast-tissue.' The outer bark was usually thick, of dense and almost indestmctible cellular tissue. The trunk, when old, lost its regular ribs and scars, owing to expansion, and became furrowed like that of an old exogenous tree." It will be understood that this statement refers to the main stems of the ribbed S'igiUarke of the type of 8. renifotints and S. Brownli, so abundant in the coal-formation of Nova Scotia, and that it is made with especial reference to the conditions of the accumulation of coal in that province. The evidence on which it is based may be stated under the follo\\dng heads : — Erect Trunks. — The numerous erect stumps of SigillaricB occur- ring at the South Joggins, and at Sydney, Cape Breton, are usually preserved as casts in sandstone, the only part of their organic sub- stance remaining being the outer bark, which exists in the state of compact coal. Still the interior structures have not altogether pe- rished, but may be recognized as a laj'or of mineral charcoal in the bottom of the stony column, under the sand and other foreign mat- ters 8ubse(]uently introduced. Occasionally the bark of the tree has collapsed before it could be filled with sediment, and the only re- mains of the trunk consist of the little mound of carbonaceous mat- ter derived from the tree itself. Cases of this kind are mentioned in my paper on the South Joggins*. In addition to the coaly mat- ter showing structure, we can also occasionally find in the interior of such erect trees a transversely striated sandstone east {Sternhenjia) representing the medullary cylinder. In one instance only have I found the medullary cylinder calcified in such a manner as to show its structure, and surrounded by the woody cylinder also in a calci- fied state. This specimen was that described, but not adequately figured, in my paper on the Structures in Coal, and I now propose to figure it more in detail (Plate X.). Ordinarily the coaly mass consists of confudcd fragments of mineral charcoal derived from the wood and the fibrous tissues of the bark ; but these often retain their structure very perfectly. After collecting and examining the woody matter thus remaining in twenty or more of these erect trees, I have found that, with one exception, it consists of tissues of a uniform character, presenting only such difFercnces as might be expected in trees generically allied. The tissues observed are discigerous or porous wood-celLs with from one to four rows of pores, pseudo-scalariform tissue, and elon- gated structureless cells of the bark (the "bast-tissue" of my former papers). These structures indicate that the woody parts of these trees were identical in character with those of the calcified axis above mentioned. * Quart. .Tourn. Gpol, Sop. vol. x. p. 1. DAWSON — SIGILLARIA, CALAMITES, AND CALAMODENDRON. 149 Tho exception above referred to is, that in one tree, which from its nijirkings 1 sujjposed to be a SujillHrIa, tho woody tissue was com- posed of larjifo cells, with many rows of pores (" multiporous tissue " of ray former pajjors) of tho ty])e of that to which Trof. Williamson has given tho name of JJictifo.ri/lon*. Since, however, as Prof. Wil- Kamson has well shown, such tissue may be regarded as a modifica- tion of tho discigerous variety, and since Corda long ago found it in the axis of a species of iStii/ttutriaf, there is nothing improbable in tho supposition that we have hero merely an indication of a spccitic or ■ubgeneric difference coming within the limits of the genus Si(jilU{ria, as at pr<;sent understood. It is to be observed that most of the erect trunks in tho cool-for- mation have not preserved their external markings with sufficient distinctness to allow the species to be determined by the leaf-scars ; but they show in most cases the characteristic ribs and rows of punctures or areoles, modified in the manner wliicli is usual in tlio case of old trunks of these plants near their bases J. In riate VIII. figs. 12, 14, 15, 10, 1 have represented some of tho more usual forms of tissue in the erect ^igiflari. — The fine apociracn of the axis of an erect Sif/iVark already referred to sliows that the pith of these trees was of that transversely laminated character which ^Wos rise to the fossils known as fStcrnhc.vtjiic. Hence we may suppose that some at least of the numerous casts of f^^teniher^ihv found in the Coal- formation have been derived from Sif/illaricr, ; but this can be ascertained only by a careful microscopic examination of the remains of woody mat- tor clinginf^ to the casts. The results of the study of a considerublc number of specimens may be stated as follows : — {<() As Prof. Williamson and the writer have shown, some of these Stet'nhcr(/!a-\nt\is belonj? to coniferous trees of the }2;eim3 D(t- (lo.vi/hn. Plate VII. fig. 1 represents a beautifully preserved cylinder of this kind enclosed in the wood of Dadoxi/Ion muteriarum. {!>) A few specimens present multiporous tissue, of the typo of Dictijo.ri/Inn, which, according to Williamson, has a Sternberg ia-\)\t\i. Plate VII. fig. 4 affords an instance of this. ((!) Other examples show a true scalariform tissue, comparable ^vith that of LcphJophJoios or Lepuloilendron, but of finer texture. Corda has shown that jjlants of the type of the former genus (his Lomatophhm) had Sternher/i!hria with Stern- herf/ia-])ith (fig. {)), of great beauty, and not dissimilar from those sometimes found in the erect S!,j!ll(n'ia;. The tissue enclosing it was unfortunately imperfectly preserved, but had three rows of pores (fig. 9 a). JStrm-tures !n Coal.— The constant association of SifjiUarla with the beds of coal, in the underclays, in the roof-shales, and in the coal Itself IS too well known to require any detailed refenmce ; and the inevitable conclusion that the Su/ilhma^ were tlic principal plants concerned in the accumulation of the mineral fuel of the true coal- measures IS generally accepted by geologists. It would naturally toiiow from this that tissues of Sii/illaria should be more abundant in the coal than those of other plants. Accordingly, as I have shown m my paper on the " Sfninh.roa ir. Coal " ■ the un vr "^y P^lfr on the "Structures in uoai,' and on .... Conditions of Coal-deposition," tissues similar to those above described are those which actually occur most abundantly in the 3ral charcoal of the coal-seams. Thnf nf f>,„ uk„ (i\.L,.. Knvi- minen • ^ , ,, , coal-seams. That of the liber or fibrous bark n^lT "^^^^'^^""^^^"t of all, and that of the woody axis the next m trequency of occurrenee. ^ It diadj the mc as porol fereil in ap woocT belo^ deni of til tion^ in tl that strei deve root! migl (6.) the DAWSON — SIOILLARIA, CALAMITE8, AND CALAMODENDRON. 151 It has been held to bo an objection to the identification of tho (Badgorous tissues above mentioned with those of ISir/illarin, that the iStif/marlce, when their structure happens to bo preserved, show merely scalariforra tissue. To this it may be answered : — (1.) That, as Corda has shown*, some Stlf/muriie have reticulated or multi- porous tissues. (2.) The tissue of lSti(jm) A very thick inner bark, which has usually in great part perished, or been converted into coal, but which, in old trunks, contained a large quantity of prosenchymatous tissue, very tough and of great durability. This "bast-tissue" is comparable with that of the inner bark of modern Conifers, and constitutes much of the mineral charcoal of the coal-seoms. (c) An outer ligneous cylinder, composed of wood-cells, either with a single row of large bordered pores J, in the manner of Tines * Ileitriige zur Flora der Vorwelt. t Brown, in 1847, described, in the ' Proceedings' of this Society, Stigmaria- roots of Lepidodendron. Baily seems to have .siiown that such roots belong to the singular Lepidodendroid Cijclostigmi of the Devonian of Ireland; and Schinipor asserts a connexion of Stigniaria roots with trees which he refers to Knorria. t These are the same with the wood-cells elsewhere called discigerous tissue, and to which I have applied the terms uniporous and multiporous. The mark- ings on the walls are caused by an unlincd portion of tho cell-wall placed in a disk or depression, and this often surrounded by an hexagonal rim of thickened wall ; but in all cases these structures are less pronounced than in Dadoxylon, and less regular in the walla of the same cell, as well as in different layers of the tissues of the axis. ir>2 1'1U)CEKI>IX08 OF THE GKOLOOICAL SOClTrTT. ami Cycads, or with two, three, or four rows of such pores Bome- times iiiHcribed in hexagonal ureoles in the manner of Datloaiilon. This woody cylinder is traversed by medullary rays, which arc short, and comiwhcd of few rows of cells superimposed. It is also traversed by obli(iue rudiatinf; bundles of pscudo-scalariform tissue proceeding; to the lenves. In some Si^lllario' this outer cylinder was itself in ])art conii)osed of psendo-scalariform tissue, as in Brong- niart's specimen of tS. tle(/aii8 ; and in others its jdace may liave been taken by nnilti\)orous tissue, as in a case above referred to ; but I have no reason to believe that eitlier of these variations occurred in tho typical ribbed species now in (luestion. The woody fibres of the outer cylinder may be distinguished most readily from those of Conifers, as already mentioned, by the thinness of their walls, and the more irregular distribution of the pores. Additional characters arc furnished by the medullary rays and tho radiating bundles of Bcalariform tissue when these can be obseiTed. (d) An inner cylinder of pscudo-scalariform tissue. I have adopted tho term pscudo-scalariform for this tissue, from the con- viction that it is not homologous with the scalariform ducts of Ferns and other Acrogens, but that is merely a modification of the disci- gcrous wood-cells, with pores elongated trjmsversely, and sometimes separated by thickened bars, corresponding to the hexagonal arco- lation of tho ordinary wood-cells. A similar tissue exists in Cycads, and is a substitute for the spiral vessels existing inordinary Exogens. (e) A largo medulla, or pith, consisting of a hollow cylinder of cellular tissue, from which proceed numerous thin diai)hragm8 to- ward the centre of the stem. The structures above referred to may undoubtedly exist in dif- ferent proportions in different species, and also in the same sjjccics in different parts, and at diflerent stages of growth. In the woody axis more particularly, there is evidence that in such forms as i^. (Faimlarla) elajam, the scalariform, or pscudo-scalariform, tissues were predominant. In young stems also, and in roots, this would probably be the case; and in the latter the texture was much coarser than in tho stem; and, further. Prof. Williamson has shown me specimens from the Lancashire coal-field, which I have no doubt are Higillarioid trees of the tvpe of S. vascularis of Bin- ney, and which, instead of a iSternherf/id pith, have scalariform cells and vessels m the centre, and in which the bundles of scalariform vessels traversing tho wood are included in considerable masses of cellular tissue, elongated vert cally, like medullary rays. This plant presents external markings of the CJathraria -tyxie. Mr. tarruthers has also shown me a specimen ribbed externally, and apparently a S^giUarla ot ^,,nmjodendron, which shows only a cylinder of krge scalariform fibres similar to those of Stujmaria. Ihesc facts show how wide differences may exist in the structures of stems referred by their superficial markings to SigUlaria. in the case of specimens showing structure merely, it will un- doubtedly require much further investigation to enable us always to DAW80X — 8I0ILLARIA, CALAMITE8, AMD CALAMODENDRON. 153 inguish the structuros charactenstic of the subgenera of Si(jil- ria, or absolutely to separate those from those of cerUiiu peculiar •onifers on the one hand and from those of the higher acrogens on the other. Young and succulent stems of Dado.n/lon may have much resembled >SI(jillarla in their structure. Young stcnis of Biy'dlaria proper may have approached closely to those of Favu- Jaria ; and since I have shown* that the branches of Favularia lesemblo Ckithraria in their scars, this last may have presented a still feebler type of internal organization. Further, there is, as I have already stated, reason to believe that some of the 8i)ecie8 referred by palueobotanists to the Clathrarla-diviBion are really forms of LepklophhioH, These difficulties, in connexion with the defective state of preservation of specimens, may excuse many diii'er- encesof opinion, though 1 think the facts already stated in this paper are sufficient to put all students of the subject on the right track in regard to at least one leading type of theso plants, and to remove some of the more fruitful sources of error. We may now proceed to incjuiro what light the structures of SigiUaria throw on its affinities. On this (luestion, taken in its most general aspect, there have, I believe, in modern times been only two opinions, the views as to alliance with Euphovbim and Cacti held by some older botanists having been given up. Some botanists, conspicuous among whom is lirongniart, hold that Siyil- larice were gymnospermous plants, allied to Cycadacea). Others are disposed to regard them as acrogens, and as closely related to Lyco- podiacea). In favour of the latter view may be urged the apparent associa- tion with Sic/illaria of certain strobiles resembling those of Lepklo- phloios, the points of resemblance between the tissues of Favularia elegans and those of Lejndodendron, and the resemblance of certain SnjillaricB, or supposed ISigillitrice, of the Clathraria-iy\}Q to Lepido- phloios. In favour of the former view, wo may adduce the exogenous structure of the stem of iSigiUaria, and the obvious affinity of its tissues to those of Conifers and Cycuds, as well as the constant association with trees of this genus of the evidently phanerogamous fruits known as Triyonocarpum and Cardiocurpum. On the other hand, the resemblance to Lepidodendron may be shown to depend merely on comparisons of a part of the tissues of Sit/UIaria with those of that genus. Grave doubts may also be entertained as to whether strobiles of Lepidophloios, and even stems of that genus have not been improperly mixed up with Sii/iUaria. It is probable that all botanists who have studied these plants, might agree that, if not Gymnosperms, they at least present points of affinity with them, and might bo regarded as in some sense a link connecting them with Acrogens. Supposing this much to be admitted, important questions remain as to their possible relations to the modern Conifers and Cycads. The higher Sigillarue unquestion- * " Conditions of Deposition of Coal," Quart. Journ. Geol. Soc. vol. xiii. ^ 130. 154 PU0CEi;i)IN09 OF TUK OEOLDUICAL SOCIETY. ably rcHcniblc Cycads in tho Btructnro of their Htoms. Their long ri^id iiiurow k'livos nisiy ]»o coinpiiivd to siiiglo piiinio of tho loavi's of Cycads. Their cord-liU*' '-ootU'ts, jis 1 have ascertained hy actual comparison, are similar to those of (lycads. If tlu-ir fruit was of the nature of Cdrdlocarjnim or Trit/oiuicarpxm, this uIbo would corre- spuiid. They differed prineipally in the division of the stem holow into those remarkable underjiround branches, tlie Sfli/tni(((ij)hlolosi\m\ LhlQih'tihintc..l.omT:^^^^^^^^ doubt whether tho proper Wala DAWSON — 8IGILLABIA, CALAMIXES, AND CALAMODENDRON. 157 "^Oalamites, but of Cahmodemlron, rests on different grounds, and is -(iopported by the fact that some of the larger stems which may bo ^^pposed to represent the external surface of Calamodendron, have tomid nodes similar to those of the branches of Asterophitllites. i|N»m8 of this kind are sometimes found in an erect position in the ^fcal-measures of Nova Scotia, and are manifestly distinct from those 4tf ordinaiy Calamites. ' 6. The microscopic stnicture oi Calamites is not precisely iden- tical with that of Calamodendron, though the latter may be regarded as a more advanced type of the former. The Calamites have a thin outer coat with lacunse, or air-ceUs, like those of modern Equiseta ; and the tissue intervening between these contains largo vasiform tabes marked on the surface with numerous rows of small pores /** multiporous tissue " of my papers on the Structures in Coal, OMJ.), ai, 1 which bear some resemblance to the fibres of Dicty- ■oecylon as described by Williamson (PI. IX. fig. lU). This struc- 'tnre has been illustrated by Goeppert, linger, Schimper, and others ; snd I have verified it by the microscopic examination of numerous fattened Calamite-stems in the shales and coarse coals. Facts of this kind kind were mentioned in my paper on the ' Structures in .€oal.' The Calamodendra, on the other hand, are casts of the medullary cavities of stems having a thick Avoody envelope disposed in wedges ileparated by intervening tracts of cellular tissue, which, according to Williamson, are of the nature of large medullary rays, while tmaller medullary rays occur in the intervening wedges, and pre- senting the same discigerous and pseudo-scalariform tissues ob- Iferved in Sigillaria. I have represented in Plate IX. two forms of 'Calamodendron with the tissues found attached to them. These stems, no doubt, have lacuna? like those of Calamites, and resemble 'tiiem in general arrangement of parts, but differ in the much greater developm.ent of the woodj'^ tissue, and, in some species at least, in the character of this tissue. 6. The fructification of Calamites I have not found in connexion with the stems. I have no doubt, however, that some of the spikes of fructification described by authors as the fruit of Calamites, really l)elong to these plants. There has, however, been some confusion between the fruit of Calamites and Asterophyllitis, A\hich demands attention from those who have access to the specimens. It results from the facts above stated that the true equisetaeeous Calamites are well known to us by their external forms, habit of growth, and foliage, as well as by their internal structure ; and on all these grounds no reasonable doubt can be entertained as to tlieir affinities. Whethf, as Schimpcr supposes, they were merely an- nual stems like those of modern Equiseta, admits of more doubt. In the equable climate of the Coal-pjriod such stems may have con- tinued growing from year to year. Nor do I think that their rhi- zomata were relatively so important as those of Equiseta. In some of the species, at least, the erect stem itself, fortified by adventitious roots, and partly buried ^y increasing depr sits of sediment, seems to I 11 I 158 rnOCEEDINGS OF THE GEOLOGICAL SOCIETY. have served the purpose of a rhizoma*. The best example that I have seen of the rhizoma of a Cahimitc is that figured in Plate IX. (fig. 21), from a specimen presented by me to the Geological Society many years ago. With regard to Calamofhiidron the difficulties are greater, and have been vrell stated by Trot. Williamson in a recent paper in the * Memoirs of the Literary and riiilosphical Society of Manchester't, in which he describes under tlie (generic name Galftmopitiis a peculiar stem, which, while he identifies it in its general cliaracters with Calmniten, he justly regards as being in internal structure distinct from the Cahnnodcndra described by Cotta and Binney. The characters of Calamodemlroa as distinguished from ordinary Calamltes may be summed up as follows: — {(() The part usually preserved is the internal axis, corresponding to a Sternheryia. It presents ribs similar to those of Cahimites, but more angidar, and almost always having traces of woody fibres capa- ble of showing the structure on some part of their surface. 1 have not seen on these casts any distinct traces of scars or areolcs. These casta of the pith of Cahnnodeadron constitute the greater part, if not the whole of the specimens referred to C. (qyproxlmatus. (h) More complete specimens are ii vested witli woody matter, arranged in wedges, and consisting of elongated cells and porous, discigerous, or pseudo-scalariform tissue. My specimens do not show distinctly the arrangement of these; but this has been well described by other observers. Williamson describes medullary rays in the woody bundles in addition to the large cellular tracts inter- vening between them. (c) The actual external surface of Cidamodcndron is not certainly known ; but I have been disposed to regard as of this kind those nbbed stems, found in the coal-formation, which have swollen nodes as if caused by the emission of whorls of small branches. I have specimens of these in my collcrtion, which I have hesitated to name or describe untd they could i>e better understood. Prof. Williamson s clescription of C(damopi(m now inclines me to 8upi)0se that they be- long to that genus or to allied forms. With regard to the aifinities of the Calamodendra, the structure of the stem raises them above tlie Calamites and modern Emiiseta, and .1 istihcs the conicoture of Brongniart that they may have been gymno- tC" '"^"ni«o"' Carruthers, and Jiinnev, however, attribute to frl,«''^'^ >''?'"''' fr^ictification. In this case they may, as the m^l If 1 ; ^' f ««"«^t'tinj.^ link between Acrogens and Gymno- throw an n^T ^}^^^«"l"^'nt investigations eon finn this view, it will C^,lIJl onT"'^ YK'"" '^'' ^''''^'^' ^ffi"ities of Sl<,dlaria. di "ncth orv J '"' ^'"^^' ^^^ r^mdodendron on the other, arc tr3iStt™w '^'^ ""'' ^^^^^"^ to, or included in, the mo- seel tTtn?n^^'"''^T^ ^"^ Lycopodiacea). But Calanwdendron %X,t " d iHr'^"^ ^''^ ^^t^'^'^" ^^"^-'-•^'^^ -"d the ribbed J ana, and m hke manner LepidopJdoios seems to connect the m ^M' * '^"X.1w &'^ ^^"^- '''^''^- «-!■ Soe. vol. X. I i BlHMJ— l c that I late IX 1 Society DAWSON — SIGILLARIA, CALAMITE8, AND CALAMODENDRON. 159 idodendra with the SifjillaricB of tho Favulnria-ty])s. On the er hand, as already stated under Sigillaria, the ribbed Sviillarice ,ay be related through Ormo,v>flon and Dadoxylon to tho modem nifcrs, and the Faindainiv may be related to the Cycads. This rc- ioiiship may be expressed as follows: — 1 Cycadacece. Conifero'. Dadoxylon. >r Favularia ? Palieoxylon. Ormoxylon f. Dictyoxylon. 8io] [LLARIA. Rhytidolepis. Calamodendron. tv Favularia ? Calamopitus. Clathraria. Eornia. Syringodendron. Calamitcs. ^ Lepidophloios. Equisefacece. (; Lepidodendron*. Lycopodiacece. I do not give this Table with any view to theories of derivation, but merely as an expression of probable affinities among tliese very curious and ancient types of vegetation. I may add here a few words with reference to Sjdunnplyllmn, a genus which some authors unite with Calamites. 'I no verticillate, Cuneate, veiny leaves of this plant, and its spikes of fructification have long been known ; and in ]8()e5 I was enabled by a specimen in the collection of Sir W. E. Logan to determine the structure of its stem, which contains a slender axis of reticulato-scalariform vessels of the type of those in Tmesipter'n^X . These i)lants obviously had no connexion with Ccdamites or Calamodendron, but constitute a peculiar synthetic type, presenting points of resemblance to Ferns and Marsiliacea). In conclusion, and with reference to my former papers on tho ** Structures in Coal," I would repeat the statement made in those papers, that the tissues of ShjiUarla, as defined in this paper, and of Calamodendron enter more largely than any others into the compo- sition of the mineral charcoal, and other parts retaining structure, of the coal of Nova Scotia ; and I have reason to believe that similar tissues arc at least very abundant in the coal of this country. Supplementary Note. — Owing to the delay in the publication of the above paper, it is necessary to add the following statements : — (1) Trof Williamson has described another type of Calamitean Btcm, which he regards as intermediate between his Cfdamopitus ami Cedamodendron §, but wliich has the retieidated or nudtiporoxs vessels of the former. To Prof, Williamson is due the credit of recogn'-'Mig this structure for the first time in English specimens, though, as lIjvo * Inpluding Sagcnaria. t Dawson, MS. X Quart. Joiini. Geol. Society. May IHOO. i Manchester Lit. and PLil. Soc. rroceedings, 1870. llNi* J i IGO PROCEEDINaS OF THE QEOLOOICAL SOCIETY. stated, it had previously been well known elsewhere. I regard these % plants, 80 well described by Williamson, as true Calamites, in tlie ". sense in which that word is used above. (2) Thi> sjimo palieobotanist lias independently expressed the k- lief above stated, that the leaves of Calamites are distinct from those oi Axtcro/ihiiHites, i\m\ has also stated a distinction between those so- called Volki)iiitnii

Sl:/lllarl(r above described. I (;i) Schimpcr, in his ' j'alcontolo^ic Vegetale,' vol. xi.,has treatei \\\ii S!) Attention haviiig been directed by Prof. Huxley to the pre- senc'G oii spore-vKscs in Coal, I have endeavoured to show, in a paper in the ' Ameiican Journal of Science ' for Ajjril, that these bodies are "^^.^Jf^^S« constituent of ordinary Coal, and that any importance which they possess in this respect is due to their identity in chemical composition with those cortical and cpidennal tissues which, like the siibenti of cork, are more nearly allied in composition to Coal than any otlier recent vegetable matters, and better titted, by their che- mical and mechanical properties, for its production. Wg- EXPLANATION OF THE PLATES. Pi-ate VIL Fig. 1. Sfen,hm,ia, pith „f Baduxi/hm; l"«, soction of one side, showing uiapiirayms ; 1 /,, section of a diaphragm and throo wood-cells, W walls ^' ^^^ wood-cells, highly niagnilied, showhig reticu- "■ ^'tisstT' f^^'?^ SiijUlaria, natural size; 2 a, 2b, diseigerous nsHuo ni vesting the same. ■ -SSint^.;' ^'^'''"'''^' "^'"^'^^ «'-: 3 a, discigerous and J. ^^vrnhmjia, natural size ; 4 «, retieul. • ^'^^^^'^"form vessel of Lepidophloios. Fig. 7. Sfer>,hergia of T.ni a ^'''''"^ ^'"I- tissue ' ^°P'^droid tree?, natural size; 7 «, scalariform _ ^'^^^oii^^lll^'^Sf^^^^l^^^ 1 ^"ot in diameter, converted iiato-scalarifonn tissue. scalariform and reticulato-scalari- Manehester Lit. and i^^C^^Zi;^^^^^;:,^;^-^^^!. ?ard the* Kin the 3d the be- Ironi those |i thu.se 90- Cnlamila described i otherwise ' lio roots of DAWSON — SIOILLARIA, CALAMITE9, AND CALAMODENDRON. 161 Wig. 9. Stcmhergia, pith of the same, natural size; 9rt, discigerous tissue of the same. 10. Another stem, probably Conifprous, w'.h Stembergia pith. 1 1 . Woody tissue of j)ro8trate SigiHarin : 1 1 «, bast-tissue of the same. 12. Woody i-issuo of a Sigillaria; 12 <^ medullary ray. l.'{. Tissue of a Sfernhergia similar to fig. I). 14, 15, 10, Discigerous tissue of erect trees {Siyillar'ue) in mineral charcoal. Plate IX. , Fig. 17. Calamndendron approximafmn, cast of pith; 11 a, lib, discigerous and Hcnlariform tissue of the same. 18. Calavwdcndron invested with woody tissue : A, pith ; B, woody cylinder ; 18«, cross section; 18/>>, cross section, magnified, showing compression of the tissue ; 18 c, discigerous and pseudo-scalariform tissue of the same. 19. Portion of a multiporous vessel of a true Calamites, magnified to the same scale with figs. 17« & 176. 20. Stem of erect Cidamodendnm (S. Joggins, Nova Scotia), showing its external surface, one-third nat. size. 21. Base of stem of Calamites (S. Joggins), showing rhizoma, reduced. 22. Node of Calamites, showing scars of verticillate branchlets and of radial processes, Plate X. ]l%. 23. Eadial section of stem of Sigillaria of the type of S. Brownii, Diiwson, restored, natural size: «, pith; h, woody cylinder ; c, cellular inner bark ; d, fibrous bark ; e, outer cortical layer. 24. Radial section of the woody cylinder, magnified (letters as above) ; and portions of the tissues more highly magnified below : h], inner pseudo- scalariform cylinder; b'l, 3, 4, discigerous outer cylinder. 25. Radial section, more highly magnified, showing one of the radiating bundles of vessels (this section has been inverted) ; 2a «, single pseudo- scalaril'orni vessel from radiating bundle. ■ 20. Tangential section of the same stem, showing the woody fibres and one of the radial bundles, and the medullary rays. > 27, Tangential section showing woody fibres and medullary rays, more ' highly magnified. 28. Radial arrangement of wof)dy fibres, magnified. • \ir^ 2',). Fibres or elongated cells of the bark {d). Note. — All the drawings oi scparafe fibres and vessels m the above figures are on one scale. Tf- I :h iilli tc L Quart. Journ.Gcoi l,ocMo\ XIVll. PIVIL W:&.Siin.1iL IMi Mnitcni J''!''-' imr. STERKBERGIA 1 \ I ) QuiLrlJourn U:ol .Soc Vc.l XXVII I'l V!l! 14 4 'I-/ 10.-.. bl^« iO .'>,, I Co? /;' A>'.f ^ s K ^ li;.S'ni brr' iitip iGirilh Idli STI'.RNBi'it^OlA \ I \ . 1 I l^k^ IX t r IL Ouafi ..loijr-ri.Cu;] I'aa: Vol XXVII 11 X. WC.linuth litli. Mitili rn Linr' irup SIG .ARIA ^