TRANSACTIONS OF SECTION C. 481 
of judging, but the true diameter of the cylinder represented by the fossil when 
uncompressed has been only 4 inches at one end of the 30 feet, and 24 inches at 
the other. Whatever its entire diameter when living, the vascular cylinder of 
this stem must have been at once tall and slender, and consequently must have 
required some ‘Appareil de soutien, such ax its exogenous vascular zone did not 
supply. This was provided, in a very early stage of growth, by the introduction 
of a second cambium-layer into the bark; which, though reminding us of the 
cork-cambium in ordinary Exogenous stems, produced, not cork, but prosenchy- 
matous cells.!. In its youngest state the bark of the Calamites was a very loose 
cellular parenchyma, but in the older stems most of this parenchyma became 
enclosed in the prosenchymatous tissue referred to, which appears to have con- 
stituted the greater portion of the matured bark. The sustaining skeleton of 
the plant, therefore, was a hollow cylinder developed centrifugally on the inner 
side of an enclosing cambium-zone. That this cambium-zone must, in matured 
stems, have had some protective periderm external to it is obvious; but I have not 
yet discovered what it was like. We shall find a similar cortical provision for sup- 
porting lofty Cryptogamous stems in the Lepidodendra and Sigillarie, 
The Oarboniferous rocks have furnished a large number of plants having their 
foliage arranged in yerticils, and which have had a variety of generic names assigned 
to them; such are Asferophyllites, Sphenophyllum, Annularta, Bechera, Hippurites, 
and Schizoneura. Of these genera, Sphenophyllum is distinguished by the small 
number of its wedge-shaped leaves, and the structure of its stems has been de- 
scribed by M. Renault. Annularia is a peculiar form in which the leaves forming 
each verticil, instead of being all planted at the same angle upon the central stem, 
are flattened obliquely nearly in the plane of the stem itself. Asterophyllites differs 
from Sphenophyllum, chiefly in the larger number and in the linear form of its 
leaves. Some stems of this type have virtually the same structure” as those of 
Sphenophyllum, a structure which differs widely from that of the Calamites, and of 
which, consequently, these plants cannot constitute the leaf-bearing branches. But 
there is little doubt that true Calamitean branches have been included in the genus 
Asterophyllites ; I have specimens, for which I am indebted to Dr. Dawson, which 
I should unhesitatingly have designated Asterophyllites, but for my friend’s positive 
statement that he detached them from stems of a Calamite. Of the internal organisa- 
tion of the stems of the other genera named, we know nothing. 
It is a remarkable fact that, notwithstanding the number of young Calami- 
tean shoots obtained from Oldham and Halifax, in which all the tissues are 
preserved, we have not met with one with attached leayes. This is apparently 
due to the fact that most of the specimens are decorticated. We have a suffi- 
cient number of corticated specimens to show us what the bark was, but such 
specimens are very rare. They clearly prove, however, that their bark had a 
smooth, and not a furrowed, external surface. 
There yet remain for consideration the numerous reproductive strobili, gene- 
rally regarded as belonging to plants of this class of Equisetine. We find some of 
these strobili associated with stems and foliage of known types, as in Sphenophyllum ,? 
but we know nothing of the internal organisation of these Sphenophylloid strobili. 
We have strobili connected with stems and foliage of Annwaria,* but we are equally 
ignorant of the organisation of these; so far as that organisation can be ascer- 
tained from Sterzel’s specimen, it seems to have alternating sterile and fertile bracts, 
with the sporangia of the latter arranged in fours, as in Calamostachys.? On the 
other hand, we are now very familiar with the structure of the Calamostachys 
Binneana, the prevalent strobilus in the calcareous nodules found in the lower 
coal-measures of Lancashire and Yorkshire. It has evidently been a sessile spike, 
1 Memoir ix. Pl. xx. figs. 14, 15, 18, 19, and 20. 
2 Memoir vy. Plates i.-v. and ix. Pl. xxi. fig. 32." 
% Lesquereux, Coal Flora of Pennsylvania, P\. ii. fig. 687. 
4 *QUeber die Fruchtihren von Annularia Sphenophylloides.’ Von T. Sterzel, 
Zeitschr. d. Deutschen Geolog. Gesellschaft, Jahrg. 1882. 
5 M. Renault has described a strobilus under the name of Annularia longifolia, 
but which appears to me very distinct from that genus. 
1883. i | 
