﻿FOLIAGE. 91 



the remaining three or four pinnules borne above it. The general condition is 

 strikingly like that shown in figure 48 of the emergent and truncated frond of 

 Macrozamia with a short petiole and rachis and nearly full-sized pinnules. The 

 mature frond of this plant, however, finally assumes an elliptical form, the pinnules 

 increasing but little in size during the final period of petiolar and rachial elongation 

 and emergence ; whence, in the absence of comparison of all the details of frond 

 emergence in a considerable number of existing species, it is not possible to deter- 

 mine from the data at hand whether or not the mature fronds of C. ingens retained 

 their prefoliate truncation. 



Regarding the insertion of the pinnules or attachment to the rachis it may be 

 noted that the pinnule bases are cut a little obliquely near the top and middle line 

 of the rachis, which does not have as prominent a middle ridge as that of most living 

 cycads. The general relation of parts is, however, the same, and the base of the 

 pinnules broad rather than rounded and stem-like, just as in most existing cycads. 

 It may be concluded, therefore, that the midrib of the rachis was not pronounced 

 and that the general appearance of the dorsal surface of the fronds of C. ingens when 

 mature and laid out flat was intermediate between that of Podozamites and Wil- 

 liamsonia, and possibly identical with one of the species of leaf imprints already 

 described under one or the other of these generic names. 



Preservation of Microscopic Features. 



Under the subject of leaf bases the general facts concerning the structure of the 

 older leaf bases of Cycadeoidca have already been given. Although as yet no young 

 leaf base and petiole of C. ingens type has been found with the cell walls naturally 

 stained with sufficient distinctness to afford satisfactory photomicrographs, or readily 

 admit drawings, the cell structure is actually present in great perfection, and it is 

 believed that artificial staining methods similar to those employed by Lignier (79) 

 may yet be resorted to with success, should naturally stained and differentiated sec- 

 tions not finally be found. The coloration or lack of coloration of the specimens is 

 not always uniform, so that clearer sections than those thus far made will doubtless 

 yet be secured. Nevertheless enough may be seen to determine that the bundle 

 pattern outlines a heavy V, very nearly or wholly like that seen in another species, 

 represented in figure 52. The coloration of the cell walls in the pinnules is 

 much more distinct, although the general tone is rather light. It is, however, clear 

 that cell preservation in the pinnules, barring the very slight lack of color differen- 

 tiation in the sections thus far obtained, is also distinct and complete. 



It has been already explained how the transverse sections of the folded fronds 

 virtually present numerous serial sections of the pinnules. This fact, coupled with 

 their fine preservation, makes the study of their main anatomical features an exceed- 

 ingly simple and satisfactory one. Even in the naturally polished sections from 

 the lateral trunk surface most of the details may be made out with the aid of a lens, 

 nearly every bundle outline being distinct, and the coloring of the larger tissue 

 zones often of most beautiful clearness. As may be seen by referring to plate xix, 

 photographs 3 and 8, the preservation and coloring of the transverse frond sections 

 of trunk 208 are the same as in the type of C. ingens. In both instances, since 



