378 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1907. 
number and position of the bracts and sporangiophores, some of the 
latter being apparently in distinct verticils, alternating with those of 
the bracts. The anatomical characters seem, however, to show an 
original relation of these sporangiophores as ventral lobes of the 
bracts. In several of the types spores of two kinds are observed. 
Pothocites, the cone of Archwocalamites, has only scattered bracts, 
while the cone of E'quisetites Hemingway? is in its superficial char- 
acters distinctly Equisetaceous. 
The general morphological agreement between the Equisetales and 
Sphenophyllales is manifest, as shown by the articulated stems with 
constant verticillate arrangement of the appendages. Archwocala- 
mites, the oldest of the known Equisetales, distinctly approaches the 
Sphenophyllales in the superposition of the verticils and in the 
dichotomously divided leaves. In many Calamariacez the individ- 
ual leaves resemble the leaves or leaf-segments of the plurifoliate 
Sphenophyllums so closely that the external characters scarcely allow 
of a distinction between the two groups. 
These, however, are only outward resemblances. The anatomical 
study of the mode of origin of the leaf bundles and of the structural 
changes attending an increase in the number of the leaves affords 
grounds for believing that the numerous leaves of a Calamite, like 
those in certain forms of Sphenophyllum, represent the segments of 
a smaller original number. The agreement in the vegetative organs 
of the two classes appears on the whole sufficiently close to be indica- 
tive of real affinity. The difference in the structure of the stele is 
undoubtedly great, but there are some indications of intermediate 
forms. 
When we come to the fructifications the agreement is more strik- 
ing. The detailed structure of the sporangia is very similar through- 
out the two groups, and the resemblance extends to the sporangio- 
phores, which in the case of Cheirostrobus, in particular, are prac- 
tically identical with those of Calamostachys; in the bisporangiate 
Sphenophyllales the agreement is still evident, though it is naturally 
diminished in the Sphenophyllum Dawsoni type, where the sporan- 
giophore has only a single sporangium to carry. 
Throughout the Sphenophyllales the sporangiophores appear as 
ventral lobes of the sporophyll, while in one species the dorsal lobes 
are also enlisted for the same service. There is anatomical evidence 
that in Calamostachys and Palewostachya the sporangiophores are the 
more or less displaced ventral appendages of the bracts next below 
them on the axis. The /L'quisetum type of strobilus (already repre- 
sented in the Paleozoic flora) appears to present difficulties, but they 
are not insuperable. In Sphenophyllum fertile both dorsal and ven- 
tral lobes of the sporophyll are fertile, and if the same displacement 
