﻿2 3° 



RELATIONSHIPS. 



latter case several of the members of one or several spirals might have been lost, jnst as 

 in C. Jenneyana there may be several less than thirteen fronds. The antecedent spiral 

 of the disk would probably be the same as that of the bracts at the time the disk first 

 formed. However this may be, the bract spirals have not yet been determined, and 

 it appears that organization into a disk preceded by spirally arranged bracts with 

 the subsequent prolongation of the main floral axis, either as that of a simple terminal 

 cone (or an inflorescence), is, in later geological time, mainly an augiospermous 

 juxtaposition, although it may yet prove that its seemingly isolated occurrence in 

 gymnosperms is largely due to an imperfectly known and understood fossil record. 



In any case the disk is to be regarded as an emplace- 

 ment attained by the cycadeoidean gymnosperms 

 without the loss of their cycadaceous characters ; and 

 while of evident importance in our conceptions of form 

 in hypothetical primitive and ancestral angiosperms, it 

 can not in itself be considered to indicate wide diver- 

 gence from other gymnosperms. It may be noted in 

 passing that the remarkably interesting isolated cam- 

 pauulate disk Codonotheca (139), with a six-segmented 

 sporangiferous inner surface, originally noted as occur- 

 ring associated with Neuropteris foliage in the Permian 

 of Mazon Creek, Illinois, is a fructification that must 

 be very anciently, if at all, connected with primitive 

 Cycadales, although the Neuropteris seeds (?) since 

 described by Kidston, do indicate certain codonothecan 

 analogies (137). At any rate, the true relation between 

 seeds " and the Codonotlieca micro- 

 spores (?) is likely to be established soon ; and if indeed 

 as here suggested these are respectively the mega- 

 spores and microspores of Neuropteris, they may shed new light on the origin of 

 Cordaites and Ginkgo rather than on any of the cycads. 



The megasporophylls and interspersed iuterseminal scales or abortive sporo- 

 phylls of Cycadeoidea are the most divergent and really difficult feature to 

 reconcile with other cycad structures. If each seed pedicel with the three or 

 more interseminal scales surrounding it were to be regarded as a shoot with a 

 fully reduced axis, the entire cycadeoidean ovulate cone would in a way corre- 

 spond to the ovulate cone-shaped inflorescence of Tumboa and to pedicellate cor- 

 daiteau forms ; and the amount of reduction undergone by the parts of each one 

 of the minor unisexual flowers, or rather shoots, would be great from any point of 

 view. But there is really little ground for the assumption that such a complexity 

 of structure is present, beyond the quite inconclusive evidence afforded by group- 

 ing of the interseminal scales in tufts, as only occasionally to be seen in very 

 young cones. On the whole it appears most reasonable to assign to the ovulate 

 cone the simple uniaxial form it at first sight appears to have. So viewed it 

 seems to have been derived from a cone originally much like that of the existing 



Fig. l34.-ZamiafloridanaDC. X \. 

 Monstrous ovulate cone with spor- 

 ophyll (at a) bearing a pinnule ol T> , , , 



L r 1 < , Rhabdocarhon 



the structure and torm normal to 

 this species. Miami, Florida, No- 

 vember 15. 



