VI. THE BRYALES 227 



which at first were mere appendages of the thallus, finally came 

 to be all that was left of it. The view of Goebel and others that 

 the filamentous form of the protonema is the primitive one, and 

 indicates an origin from alga-like forms, might be maintained 

 if the question were concerned simply with the protonema ; but 

 when the structure of the sexual organs, especially the arche- 

 gonium, is considered, and the development of the sporophyte, 

 the difficulty of homologising these with the corresponding 

 parts in any known Alga is apparent, while on the other hand 

 the resemblance between them and those of the Hepaticae is 

 obvious. It is quite probable that the development of the fila- 

 mentous protonema is a provision for the production of a 

 greater number of gametophoric branches. 



As to which group of the Hepaticae comes the nearest to 

 the Mosses, the answer is not doubtful. The remarkable simi- 

 larity in the development and structure of the sporogonium 

 of Sphagnum and the Anthocerotes leaves no room for doubt 

 that as far as Sphagnum is concerned, the latter come nearest 

 among existing forms to the ancestors of Sphagnum. Of 

 course this does not assume a direct connection between 

 Sphagnum and any known form among the Anthocerotes. 

 There are too many essential differences between the two to 

 allow any such assumption : but that the two groups have come 

 from a common stock is not impossible, and the structure of the 

 capsule in Sphagnum points to some form which like Antho- 

 ceros had a highly-developed assimilative system. This is 

 indicated by the presence of stomata, which, although function- 

 less, probably were once perfect, and make it likely that with 

 the great increase in the development of the gametophyte the 

 sporophyte has lost to some extent its assimilative functions 

 which have been assumed by the gametophyte. 



Andrecea, both in regard to the gametophyte and the sporo- 

 phyte, is in many ways intermediate between Sphagnum and the 

 other Mosses. The resemblance in the dehiscence of the 

 sporogonium to that of the Jungermanniacese is probably acci- 

 dental. It may perhaps be equally well compared to the split- 

 ting of the upper part of the capsule into four parts, in Tetra- 

 phis, although in the latter it is the inner tissue and not the 

 epidermis which is thus divided. 



If this latter suggestion proves to be true, then there would 

 be a direct connection of Andrecea with the ste^ocarpous 



