﻿68 VEGETATIVE FEATURES. 



It may at once be stated that in no specimen studied by the writer has there 

 been found evidence of lateral branches bearing groups of cones only without 

 intervening leaf bases, though such might certainly occur among the Cycadeoidea?. 

 In all the American specimens the cones occur as simple and single short axillary 

 or nearly axillary lateral branches ; and in the case of branching trunks, like that 

 shown in photograph 10, plate vi, it is interesting to note that the fructifications 

 borne by the main stem and branches alike are of the same stage of growth. 



CORTEX OF TRUNK 393. 



With the unsurpassed material brought together by successive expeditions at 

 hand, the hope was early conceived, in the course of the writer's studies, that the 

 difficulties in the way of tracing in detail the course of the cortical leaf and peduncle 

 traces, as above explained by Solms, might be overcome. It was accordingly decided 

 to attempt the preparation of a series of thin sections which would show whether 

 or not it is possible clearly to trace the entire course through the cortex of associ- 

 ated peduncle and leaf traces from their origin on the central stele to their entrance 

 into peduncle and leaf bases. This was done, and the results are certainly of 

 sufficient interest to merit presentation, although not entirely complete. 



The trunk selected as the first basis of this study is number 393 of the Yale 

 collection, representing Cycadeoidea Wielandi, already mentioned at considerable 

 length in connection with the subject of ovulate fructification. It is illustrated on 

 plate xxi. As may there be seen, it is very distinctly of the C. {Bcnneaites) Gib- 

 sonianus type, and bears numerous finely preserved lateral ovulate cones, in reality 

 short axillary branches, quite similar to those of the Isle of Wight specimens. The 

 dimensions of trunk 393 are as follows : 



Weight 15 kilos. 



Height 30 cm. 



Greatest diameter 26 cm. 



Least diameter 25 cm. 



Radius of the medulla 7 cm. 



Thickness of wood or xylem zone 1.2 cm. 



Thickness of cortical parenchyma- •• 1.5 cm. 



Average thickness of armor 4 cm. 



Width (tangential) of woody wedges 1.2 cm. 



The number of ovulate cones present and more or less completely intact and 

 actually bearing seeds, let us recall, is sixteen. But originally there were upwards 

 of forty, mostly belonging to the same season of fructification. Some of these, in 

 addition to the sixteen nearly complete fruits, are partly preserved, the loss through 

 exigencies of erosion from the cycad horizon having been a little more than half. 



In the study of the cortical system of the present trunk, one of the fruits to 

 be seen in the left-hand view (plate xxi), with the upper half cut away, was first 

 selected for the purpose of tracing the peduncular bundles in to their origin on the 

 xylem zone. Transverse section 251 was next cut from this fruit, which may be 

 designated as /, and then the longitudinal section 215 was cut from the basal 

 portion of the peduncle to determine exactly its insertion on the cortex. Follow- 

 ing these two sections further sections, mostly transverse, were cut consecutively 

 through the continuation of the peduncular bundle supply in the cortex. Twelve 

 of the more important of these, in most of which the main features are preserved 

 with diagrammatic clearness, are shown in figures 36, 37, and 38. Of the sections 



