﻿52 



VEGETATIVE FEATURES. 



with that of the leaf bases, and the extreme regularity of the surface of some of the 

 fossil trunks suggests that the ramental tips were subject to some form of excision, 

 much after the manner of the leaf bases. In many specimens the distal ends of 

 the leaf bases fail of preservation and are more or less exactly outlined as pits of 

 varying depth in the ramentum. 



The size and thickness of the ramental hairs, or rather scales, varies greatly in 

 different species, and in conjunction with quantity will probably be found to afford 

 within proper limitations one means of species identification that can be widely 

 used. But, needless to say, no uniform data can be secured except from sections of 

 considerable area, cut at a given distance from the cortex, and traversing in series 

 both leaf bases and bracts, in order that the true size, cell structure, and relative 

 number of the scales may be definitely determined. (In this connection, note 

 photographs 3 and 4, plate xxxvni; also plate xvni.) In the very characteristic 

 Cycadeoidea nigra the ramentum of the leaf bases is quite uniformly one cell in 

 thickness, as in C. Gibsonianus and in the tree fern Cyathea. In Cycadeoidea colos- 



sa/is the ramentum surrounding 



the young crown of leaves is often 

 several cells in thickness, but far 

 more rounded and hair-like than 

 in the other forms just mentioned. 

 In Cycadella, the very thick and 

 large ramental scales, as shown in 

 figure 1 8, represent the most robust 

 and abundant growth of ramentum 

 observed in any of the fossil forms. 

 In connection with the figure, ref- 

 erence should also be made to plate 

 xxxvni, photograph 3, since it 

 may be that the continuous layer 

 of cutin, as represented in the 

 drawing, was never present, the 

 outer cell alignment being abso- 

 lutely the same as in the ramenta 

 of the tree-fern Cyathea. In many 

 of the Cycadella trunks the ram- 

 entum borne by the peduncles and 

 young strobili droops down over 

 the surface of the trunk. The 

 general appearance may have been 

 not unlike that of an "old man" 

 cactus, and, taken with the small 

 trunk-size of this group of fossil cycads, may mean that the several species referred 

 to it grew in some drier and less favored situation than did such huge trunks as 

 are found in the eastern and southern Black Hills localities. 



Fig. 18. — Cycadella ramentosa. Type. 



Transverse section through ramentum of armor from lateral region of 

 trunk, in which were found embedded several adventitious young 

 fronds. S. 444 < 100. (Cf. S. 445, Plate XVIII.) 



