oOO TKANSACTIOXS AND PROCEEDINGS OF THE [Sess. i.xiw 



as homologous^ — the sporophyte being merely a differen- 

 tiated gametophyte. This theory receives some support 

 from the facts of apospory, the resemblance between the 

 young gametophyte and sporophyte, as noted by Treub (4) 

 in some Lycopods ; the existence of sporangia on fern 

 prothalli alongside the sexual organs, described by Lang 

 (o); and analogies with lower algie having sexual and 

 asexual stages. In regard to the latter, the gametophyte 

 and sporophyte are taken as standing in much the same 

 relation to each other as the sexual and neutral generations 

 of an CEdo(jonhi.m, for example. 



]jOwer (6), on the other hand, contends that the genera- 

 tions are antithetic, and that no homology can be instituted 

 between them, the phylogenetic history of the sporophyte 

 being a history apart, for the gametophyte was in existence 

 before there was the slightest trace of the sporophyte. 

 The latter is a new generation interpolated between 

 successive gametophytes, and has been developed to meet 

 the change in environment from an aquatic to a subaerial 

 life. Bower's theory is supported by evidence derived 

 from a magnificent series of researches on sporangia and 

 sporangiferous organs, as well as from facts observed in 

 a comparative survey of all types of sporophyte, from 

 the lowest to the highest forms. 



In the development of the sporophyte with the phylo- 

 genetic history ascribed to it in this latter theory, Mehnert's 

 principles find their best illustration. 



The first function of the primitive sporophyte was 

 spore bearing, and the simplest .sporophyte among recent 

 forms is represented Ijy a mass of sporogenous cells. 

 Later, change in environment from an aquatic to a 

 subaerial life rendered necessary the development of a 

 vegetative system. 



This was obtained by sterilisation of potential sporo- 

 genous cells, and further specialisation (Bower, 7), and 

 a series of types among the HejMticcc and Jlhisci can 

 1)0 adduced showing progressively increa.sing structural 

 complexity and physiological in)])ortance in the vegetative 

 system. 



In his theory of the stroljilus, Bower (S) traces the 

 mode in which the iiulependent spoi'ophyte of the higher 



