SUMMARY AND CONCLUSION 289 
The ancestors of the higher green plants must be 
sought among the simple fresh-water green alge. The 
genus Coleochette, the most specialized of the Confer- 
vace, 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 alge, 
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 Algae, 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, Hepatice, or liverworts, and Musci, 
or true mosses. The former are the more primitive and 
show many points of resemblance to the Chlorophycee, 
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 alge do 
to the Thallophytes. 
In the lower liverworts, the sporophyte, which arises 
U 
