224 
from the latest Devonian to the Triassic (7Tyrizygia), and are usu- 
ally thought of as having had a clambering habit, like a modern 
bedstraw (Galin), which they somewhat resemble in size and 
appearance. This slender elongate habit led the earlier students 
to conclude that they were submerged aquatics, but the presence of 
mechanical tissue in the stems (solid steel of primary wood sur- 
rounded by a zone of secondary wood), and the abundance of 
stomata in the epidermis conclusively contradict such a mode of 
life. The cones were large and varied, one being exceedingly 
complex (Cheirostrobus), and in the main resembled those of 
Calamites. The restoration of both Sphenophyllian and Pseudo- 
bornia necessarily somewhat exaggerates the size of their leaves. 
Pscudoboriia, shown in the lower left hand corner, 1s somewhat 
imperfectly known, since no structural material and only impres- 
sions of the cones have yet been discovered. The bulk of the 
specimens come from the upper Devonian of the Arctic (Bear 
—, 
Island), and the genus has been only doubtfully recognized in 
North America and not at all in Europe. The main stems were 
up to four or five inches in diameter with non-alternating ribs. 
The leaves were in whorls, relatively large in size for this phylum, 
and palmately dichotomous. The cones were long lax affairs, and 
the sum of the features of Pseudobornia suggest that it was re- 
lated to Calamites. 
The true Calamites, of which several varieties are shown in the 
right half of the transparency, were one of the dominant plant 
groups of the late Paleozoic. In the first place many were of large 
size with a thick zone of secondary wood surrounding the pith. 
Pith casts twelve inches in diameter and thirty or more feet in 
length have been found fossil, and lead to estimates of heights of 
upwards of one hundred feet with trunk diameters of five or six 
feet. The branches were in whorls at the nodes, and the leaves 
were in whorls at the nodes of the branches, giving a beautiful 
symmetrically plumose plant, much like some of our larger exist- 
ing bamboos in appearance. The foliage is of two principal types 
—needle-like (lsterophyilites) and flat uninerved leaves (Anmu- 
Calainites bore a considerable variety of cones, some of 
luria). 
large size, and both cones, woods, and roots have been found petri- 
fied, so that we possess a great deal of detailed knowledge of the 
