On the structure and affinities of Sigillaria, Calamites and Calamodendron [microform]

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[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<t'.

In riate X. I have represented the best-i)reserved axis in my
possession. Fig. 23 shows the structures in the entire stem, except
the portions of cellidar bark lost by decay. In the centre is a IStern-
bert/la-inih(a). This is surrounded by a woody cylinder (i), tho
inner part of which (fig. 24, hi) consists of scahiriform tissue pass-
ing towards the outer surface into pseudo-scalariform {b 2), reticu-
lated with pores (b 3), and discigerous (b 4). This woody axis has
medullary rays (figs. 25, 20, 27), and is traversed by bundles of
scahiriform tissue proceeding from tho imier part of the cylinder.
The outer portion of the inner bark, not seen in this specimen, but in
similar prostrate stems, is composed of elongated thin-walled bast-
cells, with somewhat obtuse ends, and of larger diameter than the
woody fibres of the axis (fig. 29). The tissues of tho woody axis
are all arranged in radial series (fig. 28).

Prostrate Trunks. — In the coarse shaly coals, and in the roof-
shales of the ordinary seams, there are often flattened stems of
SigiUaria, having the tissues partially infiltrated with carbonate of
lime or carbonate and sulphate of iron. The tissues usually pre-
served in these flattened trunks are those of the bark, and more
especially its large bundles of elongated or prosenchymatous cells
(" bast-tissue "). Of this I have been enabled to obtain very perfect
specimens from these flattened tninks. In a few instances only the
woody structure of the axis remains, showing the same descriptions
of wood-cells already referred to as characteristic of the erect trees.
Plate VIII. fig. 11 is an example of the structures in one of these
prostrate stems.

* Trivns. Royal Micro. Soc, Aug. 1809.

t Beitriige zur Flora &c. 1845, pi. xiii. Corda regards this na the structure
of 5. Jiroides, and the more ordinary variety as tliat of S. ani. hra.

\ Tlie species wliicli I have described as <S'. Brownii, Acad. ueol. 2nd edition,
may be regarded as a representative of these trees.

150

PROCEEDINGS OF THE GEOLOGICAL SOCIETY.

Stemherri'ia>. — 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<ila-]n\h9,. Some plants of this group are by external cha-
racters loosely reckoned bybotanists as ribless Su/nhria;(Chtthrariay,
but I believe that they are not related even ordinally to that genus.
Plate VII. fig. 5 represents a Sfernherf/in, with tissue partly reticu-
lated and partly scalariform. Plate VIII. fig. 7 represents a speci-
men with true scalariform tissue. Plate VII. fig. 0 is a scalariform
vessel of Lephlophhios drawn to the same scale for comparison. It
will be seen that it is of much coarser texture.

{d). The majority of carboniferous Stn'nhenjm show structures
identical with those described above as occurring in erect SI(/!Uitrl(i'.
Such Stcrnher<ii<v. and their structures are represented in Plate VII.
figs. 2 uid 3, and Plate VIII. figs. 8, 9, 13. Fig. 8 is a reduced
section of a large flattened tree, apparently a S!>/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. ^

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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<ina is not essentially dif-
ferent from tho pseudo-scalariform fibres of the stem, and is arranged
in a similar manner, showing that it is homologous rather with
woody than with vascular tissue. (IJ.) Many IS t it/ma ria; probably
belong to Favidarla and similar forms, or possibly even to Lepido-
dendroid plants t. In either case the structure would be unlike that
of the stems of Sh/illafia proper. (4.) Inasmuch as the propor-
tions of pseudo-vascular and discigerous tissue may differ greatly
in the stems of SiijlUarue, it would not be unreasonable to suppose
fhat the tissue, which is more particularly important for the
strengthening of the stem, should be absent, or in a feeble state of
development, in the root. Something of this kind occurs in tho
roots of Cycads, and perhaps, if detailed examinations were made,
might be found to be more general than is commonly 8upi)osed.
(6.) The outer part of the axis, being left exposed by the decay of
the loose cellular matter of the inner bark, may, in most cases, have
perished. In my specimen of tho axis of SiijlUaria, above described,
it is in parts much disorganized, and has disappeared, or been con-
verted into coal, on one side.

The evidence included under the above heads is sufficient to show
that the ordinary ribbed Si(jilluricn referred to in my previous
papers, possessed in their main trunks the following kinds of tissue,
in proceeding from the circumference to the centre : —

(rt) A dense cellular outer bark, usually in the state of compact
ooal — but when its structure is preserved, showing a tissue of
thickened parenchymatous cells.

{]>) 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/tn<iri<i', and in
tlie ^reat upward extension and, in some instances at least, raniiti-
cation of the stem. The former may be rej^arded as a special modi-
fication connected with their i)ecidiar habitat. The latter may be
interpreted as a modification either tending backward to the Lycopo-
diaceie or forward to the Couiferic. Since, so far as we at prcsonl
know, tho ramification prevails clp'efiy in tho lowc^r forms, the
foruKM' may be the more correct view. It is (;ven possible that the
iSiyilhti'Uf may include forms bridf^infj: over the space between the
hiji;hcr Acrogcns and the Uymnosperms. Viewed in this way, the
typical ribbed Si(/HI(iri(i' point downwards throufijh Calamodeailron
and Cahnnitesto the K(piisetaceic, and the Favuldrid- and Cldfht'drla-
types point throufih fjCi>i(((ij)hlolosi\m\ L<i>hlQih'ti<lron to Lyco{)odiacea?.
In tho upward direction their atfinities j)oint both towards Conifers
and Cycads. As our kjiowh'dge of the structure of indiWdual species
of S'ltjUland increases, we may hope more certainly to trace the links
of these affinities. It is, however, to bo observed here, by way of
caution, (1 ) that, of the ])lants reckoned among the several genera or
subgenera oi Si(/ill(iri<t', some may eventually prove to Ite gymno-
spermouH and some cryptogamous, and {'2) that, as wo shall find in
the next grcmp to have been actually the case, som(! of these i)lant.s
may, with a cryptogamous fructification, have i)rcsented a structure
of stem more compkjx than that found in modern pkints of similar
grade.

2. Calamodkndron and Calamites.

Calamitcs are among the most abundant fossils of the Carboni-
ferous period, and occur also in tho Devoidan ; and from their pecu-
har habitat and mode of growth, they arc not only jjroserved as
flattened steins, but also occur in immense numbers standing on the
beds on which they grew.

They have naturally been regarded from the first as allied to
IViuisetacea) ; and this opinion is ably and, indeed, conclusively
maintained by Schimper in liis recent work*, and has been illus-
T^^-ffi 1 -^ ^J^ I't^ccnt description of tlic fruit by Mr. Carruthers.
Uithcuities have, however, arisen from the fact that some stems
rcr-rded as Calamites have been found to bo surrounded by a thick
woody cylinder composed of discigerous and pseudo-scalariforra
tissue similar to that of tlie type of i^iylUarui above described,
borne botanists have regarded these last m distinct from the time

r!lZ T T ^r' 1'^'.''^ ^^"" "^ the genus Calamitea, Cotta, or
Calamodenclron, Brongniart ; and Williamson has recently proposed

* Palcontologie Vcgetalc. *

DAWaOX SrOTLLARIA, CALAMTTP-S, AND CALAMOnENDRON.

r-

tiii

r<hc name Cuhmopitus* for a group boliovod to bo intormediuto bo-
♦wceii Culumodeudi'on and truo Calami teH. On still other grounds,
i^ornia iind other genera or .subgenera have been separated from Cafa-
mltcs proper. Latterly Hehiniper has endeavoured to combine the view
of the KquiHotaccouH aflinities and ainiual growth of the .stems of
Calamitex with what, at first sight, seems the totally irreconcilable
(#0()dy character of tho stem of Ca la modem Iron as described by
iCotta, Dawes, and Binney.

', In all my own publications on this subject, from tho date of my
first paj)er on Cahtmites publislied in the Journal of this Societyt, I
jjiave lield that Calamites proper aro Eipiisetaceous plants, having
the (;xternal characters of their stems preserved, and that in tho lost
?es[)ect they differ from the internal Ciists which belong to Galamo-
dendroii. All my subse(iuent observations have served to confirm
these conclusions, which I would now iUustratc by tho following
considerations.

1. Tho true Cahtm'des (e.g. CSuckovii, C. cannrpformis, C. Cintii,
ike.), when well preserved, present, externally, somewhat fiat smooth

riated ribs, with distinct nodes, and having, at the upper end of
eh rib, a rounded areolc with a central dot or scar, marking tho
disarticulation of a leaf, branchlet, or root, or, in some cases, the ex-
tremity of one of those radial prolongations of the pith which have
been described by Williamson. In one specimen in my i)ossession
tht/e is a double set of marks — smaller ones on the node, aj)parcntly
belonging to the appendages, and larger marks below tho node, which
may represent the radial jjrolongations of the pith (1*1. X. fig. 22). Tho
cortical investment is very thin and dense, and presents externally
the characters of an epidermis, not showing, as in the case of ^Stern-
hetyla or Calamodendron, a coating of woody fibres externally, and
therefore cannot be regarded as a mere medullary sheath or, as
Scliimper 8U])poscs, the racmb;;ano lining tho hollow interior of the
stem. I may remark here, that erect Calamites are sometimes sur-
rounded by a calcareous or ferniginous concretionary coating which
'must not be confounded with the true sui'face of the stem.

2. The ordinary Calamites are seen to stand erect, rooted in sitti,
and attached together at the bases, or arising from rhizomata. The
.stems can be seen to bud from each other ; and the roots can bo
traced proceeding from their bases and lower nodes. Figures of erect
speciraens were given in my paper on Erect Calamites, and also in
that on the South J oggins:^ . Abundant specimens may be obtained
in the magnificent petrified Calamite brakes at the last-mentioned
locality, and, I venture to say, cannot be studied by any geologist
without producing the conviction that the erect cylindrical casts im-
bedded in groups in the sandstone must represent the tnio external
form of the plant. I have also shown, in the paper above cited, tha4;
these erect stems are crushed by lateral pressure, and broken down

* Preoccupied by Unger for certain Devonian planta.

t On tho Occurrence of Upright Calamites near Pictou, Nova Scotia, Quart.
Journ. Geol. Soc. vol. vii. p. 194.

J Quart. Journ. Ocol. Soc. vol. vii, p. 194, and vol. x. p. 1.

156

PROt 'DINGS OP THK GEOLOGICAL SOCIETY.

anu flattened at tho top, exactly as somewhat strong fistulous stems
would be. It is obviously impossible that casts of medullary cavities
could bo preserved in this manner. Neither Sternberc/ice nor casts of
the pith of Calamodcndra ever occur under such circumstances.

8. The stems of Calomites may be seen to have produced leaves
and branchlets in such a manner as to prove that they are complete
stems preserving their external surface. In my paper on the South
Joggins, I figured and described the leaves of (/*. Chtii as seen
attached to the erect stems. I have since, in ' Acadian Geology,'
figured those of C. Suclcovii, found under similar circumstances; and
I have specimens v^ ich appear to me to verify tho figure given by
Lindlcy and Hutto, jf the leaves of C. nodosus. I have also ob-
tained beautifully preserved specimens of the leaves of C. transi-
tionv, a species common to the Devonian and Lower Carboniferous.
It haa been supposed that the scars on the nodes of C(damites are
merely the marks of bundles of vessels passing from the interior to-
wards the surface ; but it is obvious that, in the case of stems actually
producing leaves and branchlets, this cannot be the true explana-
tion, though after seeing the very instructive slices of Prof. William-
son's CaLuno2ntus, kindly shown to me by him, I am prepared to
admit that in some specimens, at least, they may represent the
" medullary radii," which, as already stated, sometimes appear in
addition to the true vascular scars.

4. The leaves of Ccdamites were not, as is often stated, identical
with those oi AsterojihylUtn ; and the genus Calamocladus, in which
Schimper has placed many plants of the latter genus, is therefore
altogether unnecessary. A careful microscopic examination of the
leaves which I have found attached to Calamites convinces me
that they have distinct characters, and affords an additional link
of connexion with Etivlsetacca). The leaves of AsterojdiyUitcs proper
are flat, expanded in the middle, and with a distict midrib. Those
of Calamites are strictly linear, thick, and angled, and are be-
sides marked with transverse lines or striffi. Similar transv^-se
hncs occur on the branchlets of some modern Equiseta, and are
produced by hues of minute stomata. WeU-preserved specimens of
Lalamite-leaves have precisely the same appearance, so that they
may be compared to branchlets of Equiseta deprived of their sheath.
J^lattened leaves of Calamites, it is true, sometimes present the ap-
pearance of a midrib; but this arises either from the prominence of
the upper angle, or tho appearance of an internal axis through tho
substance oi the leaf. Unless very badly preserved, they can always
be distmginshcd from Asteroi^hyllites or Anmdaria. The connexion
3""^ /' by Ettingshausen and others, to obtain between Calamites
nr frnt f''?'^. f- ^'' ^"''" ^^^^^^ ^'^^ accidental association,
eoileslS'.' ^"^ ^''^'f^''^ leases and stems of Ccdamites from the

n^r tW li''"^ 1 "^ f^'^r^^^I^^iii^'*' The conjecture of Brong-
mart that some, at least, of the Astero^hylUtes may be leaves, not of

clul^trrS tS^^^^^ H.. appears to consis. of. or to in-

^'^^-•<U>hintc..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<p which may be re}j:arded as frnits of Calimitu
and those wlijch belonjjjid to Aftftroph)//lifes *. He hiisalso dcscribeil
a specimen of !Sti(f))iari(( showinp; the medullary rays, iind othenvise
approaciiin}^ to the structures which should be found in the roots oi
the typical >Sl:/lllarl(r above described. I

(;i) Schimpcr, in his ' j'alcontolo^ic Vegetale,' vol. xi.,has treatei
\\\ii S!</ill<(r'ui' very slij^'htly. He acMs no new lacts of importance to
their history, does not separate them from the jdunts of the genus
Lcpidophloio.'i, usually mixed with them, refers the whole to cue
genus, and places them with the Lycopodiaceic.

(4) Biniiey, in the raheontographical Society's Publications,
vol. xxiv., has descri])ed, under the name of Bowmanites camhrem.
a very interesting!: plant, which 1 regard as a typic;il member of the
group AstcropJii/IHteiv, as distinguished from Calamitcii'.

(•">) 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'<l"d^>^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

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