2i6 MOSSES AND FERNS chap. 



The Affinities of the Musci 



It is perfectly evident that the Mosses as a whole form a 

 very clearly defined class, and that their relationship with other 

 forms is at best a somewhat remote one. Sphagnum, however, 

 certainly shows significant peculiarities that point to a 

 connection between this genus, at least, and the Hepaticae. It 

 will be remembered that the protonema of Sphagnwin is a large 

 flat thallus, and not filamentous, as in most Bryineae. It is 

 noteworthy, however, that from the margin of this flat thallus 

 later filamentous branches grow out which are apparently 

 identical in structure with the ordinary protonemal filaments of 

 the Bryineae. In Andrecsa similar flat thalloid protonemata 

 occur, but not so largely developed as in Sphagnum, and 

 finally in Tetraphis a similar condition of affairs is met with. 

 As this occurs only among the lower members of the Moss 

 series, the question naturally arises, does this have any 

 phylogenetic meaning ? While it is impossible to answer this 

 question positively, it at any rate seems probable that it has a 

 significance, and means that the protonema has been derived 

 from a thalloid form related to some thallose Liverwort, and 

 that by the suppression of the thalloid portion, as the leafy 

 gametophore became more and more prominent, the filament- 

 ous branches, 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 archegonium, 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. 



As to which group of the Hepaticae comes the nearest to 

 the Mosses, the answer is not doubtful. The remarkable 

 similarity in the development and structure of the sporogonium 

 of Sphagnum and the Anthoceroteae, 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 



