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 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 

 plant to 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 provision 

 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 

 will also be noted that modifications are beginning to appear in 

 the arrangement of the chlorophyll-bearing cells, with the result 

 that they are sometimes distributed in the same favorable posi- 

 tions for photosynthesis, as you have noted in the higher plants. 

 However, the Bryophyta are only imperfectly adapted to ter- 

 restrial conditions and the entire plant body often assists in the 

 absorption of moisture and mineral substances. For this reason 

 most of them are moisture and shade plants, some indeed being 

 still aquatic, and they remain rather small and inconspicuous, 



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