354 Tlie American Naturalist [May, 



force the vegetative function on the sporophylls, causing them 

 to develop into more or less complete vegetative leaves. 



The experiments on Onoclea convince me that there are a 

 number of Pteridophytes, as well as Phanerogams, which 

 would yield the same results following the amputation of their 

 leaves, when carefully conducted, especially in those plants 

 where, during one season, the vegetative leaves are developed 

 sometime in advance of the sporophylls. Plants like some of 

 the Ly co pods would make extremely interesting ones to work 

 with, and especially in the case of some of these should I 

 expect to see a transformation of the sporophylls into vegeta- 

 tive leaves. This would be entirely in harmony with the rela- 

 tion and development of these organs. In species of Lycopod- 

 ium and Selaginella all gradations between sporophylls with 

 normal sporangia and the vegetative leaves can be found. 

 The transitional stages are marked by the gradual degenera- 

 tion of the sporangia on some of the leaves, the sporophyllary 

 character being shown only by vestiges of the sporangia. 

 Bower has shown how the strobilus of the Lycopods elongat- 

 ing by apical growth would result in the increase in the num- 

 ber of the sporophylls, and that the demand thus made on the 

 vegetative system for nutrition would result in the transforma- 

 tion of some of the sporophylls to foliage leaves, accompanied 

 by a corresponding sterilization of some of the sporangia. 

 Practically it would disturb the balance of nutrition between 

 the sporophyllary and vegetative systems, the effect being the 

 same as it would be if some of the foliage leaves were destroyed. 



In view of the ultimate purpose of this paper the question 

 must be raised here as to whether this transformation of the 

 sporophylls to foliar organs is a case of reversion, or whether it 

 is an advance of a primary organ to a secondary organ of the 

 sporophyte. It is my conviction that the latter alternative is 

 the logical and true one, that we can by experimentation dem- 

 onstrate phylogeny in ontogeny. Bower 2 has called attention 

 to the importance which must be attached to the fact that the 

 primary function of the sporophyte was not only the produc- 

 tion of spores, but an increasing number ; that the increase in 



'Ann. Bot., VIII, pp. 345-365, 1894. 



