Chapter XIV. 



Mosses and Liverworts as Links Between the Algae and the 



Higher Plants* 



The plants known as liverworts and mosses constitute a 

 group intermediate between the algae and the ferns. They 

 may be regarded as the descendants of algae which at some re- 

 mote time in the past climbed slowly out of the water and es- 

 tablished themselves upon the land. They still retain a number 

 of algal characteristics, although they have naturally, on account 

 of their terrestrial habitat, varied from the structural types which 

 were characteristic of the algae themselves. As is generally the 

 rule, it is. during their early stages that they most resemble 

 algae. All mosses and liverworts when first developed from 

 their spores, in a great many ways recall the algae. This is 

 especially true of the lower group of liverworts. 



The mosses and liverworts, embracing some five or six hun- 

 dred Minnesota species, are found for the most part in groups 

 of large numbers of individuals, for they are essentially social. 

 A moss-tuft at the base of some tree or in some crevice of the 

 rocks consists of hundreds of moss plants growing very close to- 

 gether and possibly all derived from the propagation of a single 

 original individual which had become established at that point. 

 Many of them prefer moist places and some are entirely aquatic, 

 floating freely in the water, or attached to pebbles at the bottom 

 of the lake or stream. Under such conditions they might pos- 

 sibly be mistaken for algae. It is not, however, probable that 

 these aquatic mosses or liverworts are the ones most closely 

 related to the algae, although such a supposition would seem 

 reasonable. On the contrary, they may rather be regarded as 

 land forms which have returned to the water as a secondary 

 adaptation ; for in a careful study of the plant world it becomes 

 evident that plants in the history of their development have 

 changed their habitations more than once. 



