MOSSES, LIVERWORTS, AND FERNS 



267 



252. The nutrition of mosses. The stem-and-leaf arrange- 

 ment of the mosses exposes chlorophyll to the light in a differ- 

 ent way from that which was found in the algse. With the 

 leaves arranged radially about the stem 



much more chlorophyll is exposed than 

 could be exposed in the same space by 

 a prostrate plant. The importance of 

 the stem in holding these leaves up 

 into the air, thus making the radial 

 arrangement possible, is great. The 

 expanded portions of the leaves are a 

 single layer of cells in thickness, while 

 the median portion may consist of 

 several layers. Moss plants are often 

 favorably placed for securing mois- 

 ture when moisture is abundant. The 

 whole dense growth made by the 

 hundreds of plants that grow together 

 may act as a sponge in absorbing and 

 holding water, so that at times, when 

 one is walking through mosses, water 

 runs in streams from those upon 

 which he steps. Certain mosses live 

 part or all of the time directly in .the 

 water. On the other hand, when long 

 exposed to drying influences, some 

 mosses become so dry that they readily 

 crumble ; but if not disturbed, they 

 proceed to grow whenever there is a 

 return of adequate moisture. Mosses 

 may also withstand great extremes 

 of heat and cold. 



253. Peat-bog moss. There are many different kinds of 

 mosses, and they are found in almost all kinds of places where 

 any plants grow. Peat-bog moss (Sphagnum) (fig. 205) is a 

 very striking form which, with other plants, often forms peat. 



FIG. 205. A peat-bog moss 

 (Sphagnum) 



About natural size 



