30 The Ohio Journal of Science [Vol. XX, No. 2, 



Thalictrum dasycarpum maleness or femaleness frequently is 

 not expressed until a late stage of the vegetative growth of the 

 annual shoot. The only other alternative explanation is to 

 assume that the sex has been determined at an early stage and 

 is later reversed in the vegetative tissues of the incipient 

 inflorescence. 



A General Survey of the Origin and Nature of 

 Dieciousness in Sporophytes. 



The evidence from comparative morphology indicates very 

 strongly that the first seed plants coming from the great fern 

 phylum, Ptenophyta, had bisporangiate sporophytes. The 

 living heterosporous ferns are bisporangiate, having, as in 

 Marsilea and other genera, microsporangia and megasporangia 

 developed on the same individual and even closely associated on 

 the same leaf. The fossil forerunners, the Bennettitales, of the 

 lowest living seed plants, had bisporangiate strobili, and there 

 is at present little question but that the bisporangiate Magnolias 

 represent the most primitive group of the Anthophyta. Even a 

 superficial study of monecious and diecious species must con- 

 vince any one that monosporangiate flowers are modifications 

 of bisporangiate flowers. 



Another fact that stands out prominently is that diecious- 

 ness and moneciousness have been independently derived in 

 many distinct groups all along the evolutionary series from the 

 lowest to the highest heterosporous sporoph^^tes. The develop- 

 ment of dieciousness, altho it must be regarded as a decided 

 specialization in hereditary ability, does not then depend on 

 advanced or specialized spermatophyte morphology but seems 

 to be a condition that can be readily established in a low type 

 as well as in an advanced one. This may be due to the fact 

 that the maleness and femaleness is established in an extreme 

 degree in spermatophyte gametophytes and can thus be thrown 

 over, so to speak, into the developing sporophyte which, of 

 course, contains all the hereditary factors of both parent 

 gametophytes with all their evolved complexity. 



When compared with its more primitive relatives, like 

 Magnolia, Ranunculus, or Anemone, Thalictrum dasycarpum 

 represents a type of flowering plant which has been directly 

 specialized in a low stage of evolution. The flowers have been 



