868 PROFESSOR W. C. WILLIAMSON AND DR. D. H. SCOTT ON THE 
Now as regards the general morphology, the simple leaves, arranged in whorls of 
many members, form an obvious point of resemblance to Eguisetum. In the 
specimens of Calamites showing structure, we can, indeed, only infer the position of 
the leaves from that of the outgoing vascular bundles; the macroscopic specimens 
however, leave no doubt as to the facts.* 
On the other hand, it is quite certain that the leaves were separate, not cohering 
to form a sheath, as in Equisetum. Further, the alternation of the leaves of 
successive whorls was less constant in Calamutes than in the recent genus. 
The branches of the stem in Equisetwm are alternate with the leaves of the whorl, 
in the axil of which they arise. This agrees substantially with the position of the 
branches in Calamites (see Plate 72, photographs 5 and 6, Plate 80, fig. 21). The 
relation of the vascular bundles to those of the main stem seems also to agree in the 
two genera, but this will be considered below. The insertion of the branches below 
the node in Hgwisetum is, of course, only apparent. The branches arise in the axil 
of the whorl, and therefore above it. Subsequently they become overgrown by the 
leaf-sheath, and ultimately break through it at its base. If the leaves of Equisetum 
were distinct like those of Culamites, the insertion of the branches above the node 
would be equally evident in both genera.t 
As regards the insertion of the adventitious roots, we know that in Lquisetum 
they arise from the base of the lateral branches, one to six on each branch. From 
the specimens of Calamites showing structure, we have at present no evidence as to 
the insertion of the roots. There is, however, no doubt, from the evidence of 
impressions and casts, that the roots arose at the node or immediately above it, from 
the base of the internode. Sometimes they were placed in a regular circle, some- 
times they are grouped in tufts, and these tufts may arise at the base of a branch.t 
It does not seem probable, however, that they had any constant relation to the 
branches, such as we find in Hquisetum. 
So far as our knowledge of the external morphology of the vegetative organs of 
Calamites extends, we thus find a general agreement with Hquisetum, sufficient to be 
quite consistent with a relationship between the genera, but not by itself conclusive. 
(1.) It has already been mentioned that in the course of the vascular bundles the 
resemblance to Equisetum, though evident, is incomplete; the differences consist in 
the facts that a bundle may traverse more than one internode, and that the bundles 
of successive internodes do not constantly alternate with one another (see Plate 72, 
photograph 5, and Plate 78, fig. 11). 
* See especially Weiss, “ Steinkohlen-Calamarien,” II., 1884, cap. 3, “ Beblitterung der Calamarien.” 
+ Cf. Janczuwsxi, ‘ Recherches sur le Développement des Bourgeons dans les Préles.” ‘Mém. de la 
Soc. des Sci. Nat. de Cherbourg.’ XX., 1876. His principal figures are reproduced in the modern text- 
books, such as those of GorEL or vAN TinGHEM. 
{ Wauiss, “Steinkohlen-Calamarien,” II., 1884, cap. 4, “Wurzeln der Calamiten”; LiypLey and 
Hurtoy, ‘ Fossil Flora of Great Britain,’ vol. 1, plates 78 and 79. 
