338 G. R. Wieland — Notes on Living Cycads. 



Having already discovered the pollen-bearing fronds of 

 Bennettites (this Journal, March, 1899, and June, 1901), the 

 description by Thisel ton-Dyer interested me very greatly. I at 

 once thought it probable that such cones might frequently 

 occur, and that in the case of male cones there must be great 

 likelihood of the reverted fronds eventually being found fertile. 

 A few weeks later the Zamia cone above described was 

 obtained. It is to be hoped that all such cases of reversion 

 may be recorded. They promise to relieve us of the necessity 

 for much speculation, and to be fully as important in our own 

 morphological conceptions as have been the cones of other 

 gymnosperms in the hands of Celakovsky', or probably much 

 more so, because these forms yield us a knowledge of very 

 primitive conditions. We are already in some measure guided 

 when we attempt to form an hypothesis of the manner in 

 which prothallial elimination must have proceeded in some 

 marattiaceous or older fern line ancestral to the gymno- 

 sperms. At least the series from ordinary cycadean foliage 

 leaves through the carpophylls of Cycas to the less leaf-like 

 sporophyll of the cone (simply a seed-bearing branch) of Z>ioon, 

 and the ordinary much altered sporophyll of the other cycadean 

 genera, must be regarded as a connected one. And as I have 

 elsewhere pointed out, the staminate fronds of the Bennettitese 

 afford concerning the coordinate changes which took place in 

 microsporophylls an explanatory analogy of the most striking 

 character. Progressive prothallial elimination, with correlated 

 spore differentiation and alteration of the frond-like sporo- 

 phytes of primitive ferns of the marattiaceous or an ancient 

 allied group, were the basal factors in the evolution of the 

 Cycadofilicinean and Cordaitean alliance. This subject of 

 fundamental importance I shall treat more definitely else- 

 where. 



The question of the homology or equivalency of the Cyca- 

 dean ovule to pinnules comes up in this connection. But I 

 certainly think that the testimony of other unusual cones which 

 we are almost sure to find in the course of time will be much 

 more satisfactory than any insufficiently founded speculation, 

 and shall therefore content myself with pointing out the opin- 

 ion of Thiselton-Dyer (loc. cit.) thus conservatively expressed : 

 u * # #■ * an vule is a sporangial structure, and it is not easy 

 to see anything in a pinna which is in any way comparable to 

 it. Morphological conceptions must not enslave us, and I see 

 no reason why sporangial structures, like buds, may not appear 

 anywhere." 



Yale Museum, New Haven, Conn. 

 January, 1902. 



