Chapter XVI. 



Mosses of Minnesota. 



The mosses may, like the ferns, he conceived to be the de- 

 scendants of ancestral forms somewhat similar to the horned 

 liverworts, althoug-h none of them are to-day very close in their 

 structure and life-histories to that group of plants. All mosses 

 are distinguished by the following peculiarities, in which they 

 differ from liverworts. The second-stage of the vegetative sex- 

 ual plant is in every instance a branched or unbranched, leaf- 

 bearing stem. While it is sometimes prostrate in habit this 

 position is an adaptive one and not original, as among the liver- 

 worts. Finally and most important, the young capsular plant 

 before maturity always bursts the wall of the egg-organ in which 

 it began to de\-elop and ne\er, like most liverwort capsular 

 ])lants, matures while still within that membrane. .V moss 

 capsular plant is decidedly a creature of more complicated struc- 

 ture than a li\erwort capsular i)lant and it consists, even in the 

 simple forms, of a generally greater number of cells. There 

 are, however, one or two mosses in which the capsular plants 

 are greatly reduced in size, and these would scarcely come with- 

 in the general rule. 



Mosses have acquired the ability to live in much drier places 

 than liverworts are accustomed to frequent, indicating their 

 stronger adaptation to terrestrial life. While the rock-dwelling 

 liverworts are found usually on moist cliffs or banks, it is not 

 uncommon to find some mosses growing upon the driest bowl- 

 ders, where a little crevice or hollow in the stone gives them a 

 soil upnn which their rootlets nia\' work. Such mosses are gen- 

 eral I v of a blackish green color and look very crisp, crumbling 

 easilv if rubbed with the fingers. Yet in this condition they are 

 not dead: for if moistened, they rapidly revivify and proceed 

 with their functions of growth. ( )tlK'r mosses choose very wet 



