60 Morphology BOOK i 



tion ; this in the phylum of the Bryophytes is chiefly sup- 

 plied from the gametophyte which shows distinct adapta- 

 tion to sub-aerial habit, while the means of nutrition on 

 the part of the sporophyte itself are in these plants very 

 limited and the external morphology of it very slight. In 

 other distinct phyla, however, such as the Filicinae, Lyco- 

 podinae, and Equisetinae, the sporophyte itself assumed 

 the function of nutrition ; a higher morphological differen- 

 tiation of parts followed, and a more clear distinction 

 between the organs which were to supply the nutriment 

 (stems, leaves, roots), and the parts devoted to the formation 

 of spores (sporangia), this for the first time stamped the 

 sporophyte with a character of independence and per- 

 manence.' 



The second question raised as to the necessity of assuming 

 that a sporogonium stage must have occurred during the 

 evolution of the sporophyte of the fern was not empha- 

 sised so strongly. Most writers agreed that the great gap 

 existing between the surviving Bryophyta and Pterido- 

 phyta, with the complete absence of any evidence on the 

 point arising from fossil forms, takes it out of the region of 

 profitable discussion. Lang, whose work came nearer to 

 the end of the century, held that the passage from the one 

 group to the other is quite conceivable, and said that the 

 comparison has been facilitated by fuller knowledge of the 

 structure of the simpler sporophytes of the Pteridophyta, 

 especially that of Phylloglossum, but he did not go so far 

 as to endorse the view of direct descent. A similar cautious 

 reserve is noticeable in the writings of Bower already 

 quoted. Klebs, writing in 1898, seems to have said the 

 last word of the century on the point : ' Though we have 

 gained certain connecting points for the phylogeny of the 

 Mosses, the question as regards the Ferns, in which the 

 fertilized ovum develops into the leafy plant, is in quite 

 another position . . . The spot where the first indication of 



