SUMMARY AND CONCLUSION 289 



The ancestors of the higher green plants must be 

 sought among the simple fresh-water green algse. The 

 genus Coleochsete, the most specialized of the Confer- 

 vacese, is the form which shows the nearest analogy 

 with the lower Bryophytes, which it closely resembles 

 in the development of a rudimentary sporophyte as the 

 result of fertilization, and thus shows a very simple 

 case of the alternation of generations so characteristic 

 of all Archegoniates. In the mosses this becomes well 

 marked, but there is a good deal of difference between 

 the simplest of these and the highest green algae, 

 although the persistence of the motile spermatozoids 

 indicates the derivation of the Archegoniates from 

 aquatic ancestors. 



The mosses, being mainly terrestrial plants, have 

 developed much more perfect tissues than the Algse, and 

 in the ferns, which undoubtedly are related to them, 

 this is still more marked. In both groups of Arche- 

 goniates, the reproductive organs, archegonia and an- 

 theridia, agree closely in structure, and the sporophyte 

 always gives rise to spores which are formed in tetrads 

 from a common mother-cell. 



The Mosses (Bryophytes) show two well-marked 

 series, or classes, Hepaticse, or liverworts, and Musci, 

 or true mosses. The former are the more primitive and 

 show many points of resemblance to the Chlorophyceae, 

 and they are especially important as being the primitive 

 stock from which the several series of archegoniate 

 plants have diverged, bearing much the same relation 

 to these higher Archegoniates that the green algse do 

 to the Thallophytes. 



In the lower liverworts, the sporophyte, which arises 



