MOSSES 



407 



in proportion to the sterile part than is the case in the 

 sporogonium of Marchantia. By sterile part is meant any 

 part which does not produce spores. This increase in the 

 sterile part of the sporophyte 

 is significant, for in higher 

 plants we find that nearly 

 all the cells of the sporophyte 

 are sterile. The sporogo- 

 nium of certain mosses, like 

 that of Anthoceros among 

 liverworts, contains chloro- 

 phyll and does some food 

 making. The bulk of its 

 nourishment, however, is 

 probably absorbed by the 

 foot from the tissues of the 

 leafy stem . As in liverworts, 

 the sporophyte is a parasite 

 upon the gametophyte. The 

 gametophyte in mosses in- 

 cludes both the protonema 

 and the leafy part. 



FIG. 203. A young moss plant arising 

 from the protonema and putting out 

 rhizoids. Note the diagonal cross walls 

 of the filaments. At the end of one of 

 these filaments a resting bud appears. 

 A moss plant may arise from this. 



B. Increase of the Sporo- 

 phyte. Already we have 

 noted that the sporophyte 

 becomes more prominent as we go from the simpler plants 

 to the more complex ones. At first the sporophyte is 

 only a number of spores and a case. Gradually it increases 

 in size and becomes differentiated into several kinds of 

 tissues and organs. It begins to do leaf work. We have 

 seen this in both liverworts and mosses. (See Figure 206.} 



