CHAPTER VII 



DIVISION II. BRYOPHYTA. THE LIVERWORTS AND 



MOSSES 



101. Adaptive Features of the Bryophyta. We have now 

 reached the point in the evolution of the plant where it has left 

 the aquatic condition of its algal ancestors and become largely 

 terrestrial. As has been stated, the. fungi do not enter into the 

 scheme of evolution of higher types. They are to be looked upon 

 as a side line, derived doubtless from various groups of the algae, 

 that have undergone a peculiar series of variation owing to their 

 parasitic and saprophytic habits and that are in no way connected 

 with higher plants. In the Bryophyta we take up again the line 

 of ascent. Naturally we would expect that a change from the 

 aquatic to terrestrial conditions would be attended with profound 

 changes, tending to adapt the plants to the terrestrial conditions. 

 The results of the stimulus of the new surroundings are seen in 

 the production of hair-like outgrowths, rhizoids, that anchor the 

 planfTo the substratum and bring it into proper relation with the 

 soil. So long as the plant lived in the water any of its cells 

 might serve as absorbing organs, but it is evident that the pro- 

 vision must now be made for procuring the crude materials which 

 are no longer in direct contact with the plant. The exposure_of 

 the plant to the atmosphere results .also in the formation of a 

 cuticle and of mucilage-producing cells which tend to retain the 

 moisture and so adapt the plant to its drier environment. It 

 wifi also be noted that modifications appear in the arrangement 

 of the chlorophyll-bearing cells, with the result that they are al- 

 ways distributed in the same favorable positions for photosynthe- 

 sis, as you have noted in the higher plants. However, the Bryo- 

 phyta are only imperfectly adapted to terrestrial conditions and 

 the entire plant body often assists in the absorption of moisture 

 and mineral substances. For this reason they are moisture and 

 shade-loving plants, some indeed being still aquatic, and they 



242 



