﻿BISPORANGIATE AXES. 



155 



sections tliey appear in obliquely set interlocking pairs and are short-stalked, sug- 

 gests that each filiform pinnule bears somewhat laterally two closely set distichous 

 or alternate rows of synangia. This lateral attachment of virtually sessile synangia, 

 as well as the very regular outlines of the fertile pinnules, however, appears with 

 diagrammatic clearness in the tangential section shown in plate xxxvn, photo- 

 graph 2. Each frond, including the basally fused peduncle, is about 10 cm. in 

 length in C. dacotensts, and a little less in C. ingens, the number of pairs of alternate 

 pinnules in both species being about twenty, including the barren basal and apical 

 pinnules. The longest pinnules are 1.5 cm. in length, bear about twenty syn- 

 angia, ten in each lateral row, and are borne just beyond the middle region of the 

 frond, which, when expanded, must hence have been of typically filicinean appear- 



Fig. 79. — Cycadeoidea. 

 Bisporangiate strobilus, showing how the scars left by hypothetical^ dehiscent pinnules of the staminale fronds might produce the features 

 represented in Williamson's "carpellary disk." (See preceding figure.) 



ance. Moreover, such a frond could readily result from the reduction of a bipiunate 

 form, each synaugium then representing a reduced leaflet. 



EXPANDED STROBILI. 



The expanded form of a flower such as that described is not difficult to con- 

 ceive, and in the frontispiece to this section a reconstruction is given which, 

 though based on a species with fewer fronds, doubtless very well represents the 

 general appearance of the strobilus at the time of the shedding of pollen. In this 

 restoration, however, the surrounding armor of old leaf bases is imagined as 

 arbitrarily removed, contrary to the fact that since the peduncles did not elon- 

 gate, only the distal half of the fronds could emerge when shedding their pollen. 



