﻿kxistim; and KoSSIL cycads compared. 



2 ?> l 



cycads, with a series of spirally arranged megasporophylls all fertile and alike, 

 but borne on an axis with hypogynous microsporophylls. Subsequently, if 

 this view is correct, with reduction and shortening of the ovulate axis, the orig- 

 inal spiral order has been obscured by the assumption of a very perfect radial 

 symmetry in a fertile series of pedicels and the flattening and aborting of adja- 

 cent members into iutersemiual scales.* In either case, however, the theory 

 that the seed pedicel and the iutersemiual scale are greatly reduced sporophylls 



analogous to and derived from 

 sporophylls like those of the 

 existing cycads is regarded as 

 most tenable. It is not 

 believed that there is any great 

 or insuperable objection to the 

 theory of ours that one of the 

 final reduction stages of a 

 cycadean carpophyll would be 

 a more or less pedicellate form 

 with a single, either endarch 

 or mesarch, concentric bundle 

 supplying an apical and erect 

 radio-symmetric seed as in 

 Cycadeoidea. The ovulate 

 coues of the latter are obvi- 

 ously enough of a far less 

 primitive structure than those 

 of existing cycads. 



T h e fundamental sim- 

 plicity of such a theory of 

 course rests primarily on the 

 fact that it involves the evo- 



Fig. 135. — Encephalarlos villosus Lem. Monstrous cone with more and lutioil of llO new Structures, 

 more leaf-hke carpophylls above until finally one of these metamorphosed Where new structu reS lUUSt 

 sporophylls arises as a small but distinct truncated Irond beating well-char- 

 acterized pinnules of its genus and species, constantly be invoked and 



a, Carpophyll replaced by reduced, though otherwise normal leaf ; b. generalized car- aCCOUllted for evolutionary 

 pophyll of foliaceous habit ; c, foliaceous carpophyll of arrested development ; d. a 

 normal carpophyll. (Reduced from ThiseltonDyer - 1 67.) tlieOl'ieS Uiay Well paUSe ; but 



when the result can be reached by a simple process of reduction, and when there 

 are examples of such reduction all along the line, an implied certainty is involved 

 that nature took that course. That the carpellary leaf is primitive and charac- 



*The younger the fruit the greater the difficulty of distinguishing between the infertile and fertile 

 series. Moreover, in many cases large areas normally bearing seeds are infertile and closely invested by 

 aborted scales only. Therefore, since the distribution of the infertile scales and the seed pedicels is not 

 entirely alternate and the proportion of both varies so greatly at the base of the cones, it appears that the 

 determinant change resulting in infertility must arise after the initial stages of growth. Certainly, whether 

 the ovulate axis is primarily a simple axis or consists in reality in a series of secondary shoots, there can 

 be little doubt that the interseminal scales were once fertile organs in no wise different from whatever 

 was the analogous form of the seed pedicel at that earlier time. 



