344 PRACTICAL COURSE IN BOTANY 
and chlorophyll so that it is capable of manufacturing food. 
In this respect it shows a distinct advance on the correspond- 
ing phase of the liverworts—if we except the single genus 
Anthoceros, which alone among the liverworts has the cells 
of the sporogonium provided with chlorophyll. 
400. Alternation of generations. — The process of repro- 
duction in mosses is so closely similar to that of liverworts 
that it is unnecessary to repeat the details. There are 
some minor variations, but in all essentials the processes 
are the same and may be represented to the eye by the 
same formula. 
401. Relative position of mosses and liverworts in the 
line of evolution. — Though mosses, as a rule, show a higher 
degree of organization than liverworts, in both generations, 
their development has been away from the general course 
of evolution followed by the higher plants. This, as will 
be seen later, tends towards a decreasing complexity of 
the gametophyte with increasing complexity of the sporo- 
phyte, while the mosses show increasing complexity of both. 
Like the order of birds in the animal kingdom, they form 
a highly specialized and somewhat isolated group. While 
they may be regarded as descendants from a common an- 
cestral stock with the ferns and club mosses, they have 
been switched off, so to speak, on a side track of the great 
evolutionary trunk line, and their advance on this side 
track has carried them to a point more remote from the. 
course along which the higher forms of plant life have 
traveled than the distant junction at which they branched 
off from their less progressive kindred, the humble liver- 
worts. 
VII. FERN PLANTS 
Marertau. — Any kind of fern in the fruiting stage. Several different 
varieties should be cultivated in the schoolroom for observation. While 
gathering specimens, look along the ground under the fronds, or in green- 
houses where ferns are cultivated, among the pots and on the floor, for 
a small, heart-shaped body like that represented in Figs. 501, 502, called 
a prothallium. It is found only in moist and shady places, and care should 
