94 Plant Life and Evolution 



Subordination of Spore Production in the Higher 

 Archegoniates. Among the liverworts proper, the 

 function of the sporophyte is almost entirely spore 

 production, and it develops little or no chlorophyll, 

 so that it is capable of very little independent 

 growth. In two other classes of the bryophytes, 

 viz., the true mosses and the horned liverworts 

 (Anthocerotes), the sporophyte becomes much more 

 important and spore production is to a considerable 

 extent subordinated to the vegetative life of the 

 sporophyte. In these forms the growing period of 

 the sporophyte may last for several months before 

 the spores are finally developed, and only a relatively 

 small portion of the sporophytic tissue gives rise to 

 spores (Fig. 10, C). A large amount of green tis- 

 sue is present in the outer portion of the sporophyte, 

 and this may form a spongy green tissue quite like 

 that in the leaves of the higher plants. As in the 

 latter, this green assimilative tissue may communi- 

 cate with the atmosphere by means of special pores 

 or stomata, which structurally closely resemble those 

 of the vascular plants. By means of these well de- 

 veloped chlorophyll-bearing tissues, the sporophyte 

 can assimilate the CO 2 of the atmosphere, and it is 

 quite independent of the gametophyte for its supply 

 of organic food. In some of the true mosses the 

 green tissue is largely segregated at the base of a 

 capsule, where it forms a sort of assimilative organ 

 known as the apophysis. This may be said to take 

 the place, physiologically at least, of a leaf. There 



