﻿IOO VEGETATIVE FEATURES. 



tion and frond structure, and in the main the habits of foliage-crown formation of 

 nearly every North American cycadeoidean species. The leaves of several other 

 species than those above described have already been observed, but as their characters 

 are not essentially different it is not deemed necessary in this more distinctly bio- 

 logical study to more than mention the fact that further forms are known. 



CYCADELLA. 



It has been pointed out in Chapter I that one of the most important of the several 

 American series of silicified cycadeoidean trunks is that included within the genus 

 Cycadella, as erected by Ward for the reception of the series of rather small forms 

 from the Atlantosaurus beds or Morrison formation of the Freezeout Hills of Carbon 

 County, Wyoming. As since found by the writer, trunks of the same general 

 character as the Carbon County forms also occur in relatively the same horizon of 

 the Black Hills Rim, accompanied by the skeletons of huge saurians (Barosaitrus, 

 Diplodocus, Morosanrus, Broiitosaurus, etc.) ; although associated plant remains are 

 meager in number, consisting almost entirely in numerous silicified Araucarian logs 

 and billets, with occasional imprints of fronds of the primitive cycad NUssonia 

 (194-6). This occurrence of Cycadella in the Black Hills, 150 or more feet beneath 

 the horizon in which the Cycadeoidea series of trunks is embedded, in surroundings 

 so similar to those of Carbon County, Wyoming, nearly 200 miles farther west, 

 shows the genus to have had a considerable lateral range. It is, however, of greater 

 interest that we are thus enabled to examine a supplementary genus closely related 

 to Cycadeoidea, but separated by a considerable interval of time; and among the 

 vegetative parts affording opportunity for this comparative study none are more 

 interesting than the silicified young leaves, their structure and prefoliation being as 

 exquisitely shown in this rather dwarfish genus as in the more robust Cycadeoidea. 



CYCADELLA RAMENTOSA. 

 (Plate XVIII.) 



The type specimen of Cycadella ramentosa gives no promise exteriorly of the 

 young leaves borne by its middle segment; but as figured by Ward (178), the sum- 

 mits of several fruit axes are plainly to be seen scattered over the lateral surface of 

 the trunk, whence it was supposed that a section through a small ramentum-covered 

 boss, noted on the middle of the three segments into which the trunk was broken as 

 originally collected, might yield evidence as to the fructification. On making a 

 section tangential to the trunk, however, instead of a young fruit, I unexpectedly 

 secured in transverse section several finely preserved non-emergent fronds, as shown 

 on plate xviii. These fronds are thus seen to have been borne adventitiously 

 among the old leaf bases, as just described in C. ingens (T. 208), and the fact is again 

 emphasized that the cycadeoidean trunks produced from the axils of the old leaf 

 bases, very freely indeed, either leaves, branches, or fruits. 



Prefoliation is direct and the frond once-pinnate as in Cycadeoidea. But since 

 in each of the transverse sections through the folded fronds a much smaller number 

 of pinnules are cut than in the similar sections from C. ingens and C. colossalis, it 

 is quite safe to say that the number of pairs of pinnules present is much under fifty 



