104 The Ohio Journal of Science [Vol. XVIII, No. 4, 



studied the facts of plant evolution. The utilitarian view as 

 developed to a supreme position in the Darwinian theory 

 is largely discordant with present day views, but still seems to 

 have a tenacious hold on the philosophy of sex. Things 

 may be useful but the cause of their origin and persistence is 

 another question. One can find endless cases where exactly 

 opposite developments occur side by side in closely related 

 species and varieties subject to a common environment. For 

 example, note the barbed involucral bristles of Chaetochloa. 

 In Chaetochloa verticillata (L.), Scrib. the barbs are retrorse 

 while in the closely related Chaetochloa viridis (L.) Scrib. 

 they point outward. In neither case have they any relation to 

 seed distribution since the bristles remain on the dead inflores- 

 cence when the spikelets fall. In the genus Bidens, the papus 

 awns are usually barbed, but here also some species have 

 retrorse barbs and some outwardly projecting barbs. Since 

 the awns are persistent on the fruit the retrorse barbs become 

 useful but the others, if they have any effect must rather hinder 

 seed distribution. In some species of Bidens the awns have 

 no barbs whatever. Any number of similar cases could be 

 cited. 



Sex appears in some way to be associated with physiological 

 and chemical states of the living protoplasm. It is perhaps 

 most reasonable to assume, at present, that a certain organi- 

 zation or complexity of the cell is necessary before sexual states 

 originate. But it is not true on the other hand that these 

 states are necessarily set up at any stage of the life history 

 even in organisms that have the essential complexity. 



Among plant gametophytes the greatest sexual difference 

 is shown in the Spermatophyta, between the male and the 

 female. In the Archegoniata, very striking examples are 

 certain species of Polytrichum where the mature male plant 

 has a very different appearance in form and color from the 

 female. The difference is much greater than is exhibited 

 by many mammals or even birds. Now, just as in the game- 

 tophyte generation we find no vegetative dimorphism in the 

 lower forms but find this becoming more and more pronounced 

 as we ascend the scale, so also in the evolution of the sporophyte 

 it is only the extreme forms in the evolutionary series that 

 show but the one state throughout the entire individual. It is 

 evident also that the gametophyte is far advanced in evolution 



