CHAPTER XVII 



SUMMARY AND CONCLUSIONS 



The Interrelationships of the Archegoniatce 



It is pretty generally conceded that the origin of the whole 

 archegoniate series is to be sought somewhere among the green 

 Algae, and that on the whole Coleochcete is, perhaps, the 

 form which is nearest to the simplest Muscinese. While the 

 Characeas, as we have seen, approach the latter more nearly in 

 the structure of the sexual organs, yet the character of the vege- 

 tative parts is so different from that of any of the Muscineas, and 

 the sporophyte is so simple, that any close relationship of the 

 two groups is hardly probable. At best, the connection be- 

 between any known Alga and the Muscinese is a very remote 

 one. 



From a study of the facts presented in the foregoing pages, 

 the conclusion has been reached that the Liverworts are not only 

 the most primitive of the existing Archegoniatas, but are also 

 the forms from which all the other groups have descended. 

 When, however, the question arises as to which of the existing 

 groups of Liverworts is the most primitive, the matter is not so 

 easy to settle. Thus while Riccia undoubtedly has the most 

 primitive sporophyte, the gametophyte shows a much higher 

 degree of differentiation than is found in most anacrogynous 

 Jungermanniacese or in the Anthocerotes. The latter group, 

 while retaining an extremely simple type of gametophyte, has 

 the sporophyte developed beyond that of any other Liverworts. 



It will be remembered that in the germination of most 

 thallose Liverworts (and occasionally in the foliose forms as 

 well) the occurrence of a single two-sided apical cell is quite 

 general, although this may be absent from the fully-developed 



S92 



