Bryophytes : Liverworts and Mosses 



471 



Fig. 287. The liverwort, Marchantia, showing capsules and various stagts in ihe dc\ tlop- 

 ment of the antheridial and archegonial branches. 



the tropics. Porella is a rather common example found at the 

 bases of trees, or on rocks in moist ravines. The life histories 

 of the leafy liverworts are very similar to that of the thallose 

 forms. 



MOSSES 



The mosses form a very large group found in all parts of the- 

 world. Like the liverworts, they are most abundant in. moist, 

 partly shaded habitats. A few, however, grow on rocks and trees 

 where they are exposed to intense light and periodic drought. 

 When dry, they are dormant; and when wet, they carry on 

 the usual life processes. 



As a result of their methods of vegetative multiplication, mosses 

 have the habit of growing in compact clusters. This gives 

 them an external means of conserving water and maintaining 

 the water balance. The dense masses of plants take up water 

 from rains and hold it for some time like a sponge. 



The plant body. Mosses usually have upright and radially 

 symmetrical stems, though many live close to the substratum and 



