CHAPTER V 

 THE MOSSES (MUSCI) : SPHAGNALES ANDRE^ALES 



THE Mosses offer a marked contrast to the Hepaticse, for 

 while the latter are pre-eminently a generalised group, the 

 Mosses with a very few exceptions form one of the most 

 sharply defined and specialised groups of plants known to us. 

 Although much outnumbering the Liverworts in number of 

 species, as well as individuals, the differences in structure be- 

 tween the most extreme forms are far less than obtain among 

 the Liverworts. While the latter occur as a rule in limited 

 numbers, and for the most part where there is abundant 

 moisture, the Mosses often cover very large tracts almost to 

 the exclusion of other vegetation, especially in northern 

 countries. In more temperate regions, the familiar peat-bogs 

 are the best known examples of this gregarious habit. Mosses 

 are for the most part terrestrial, and are found in almost all 

 localities. Some grow upon organic substrata, especially de- 

 caying wood, and are to a greater or less extent saprophytic. 

 Haberlandt (4) first called attention to this, and investigated 

 a number of forms, among them Rhynchostegium murale, 

 Eurynchium prcelongum, Webera nutans, and others, and in 

 these found that the rhizoids had the power of penetrating the 

 tissue of the substratum, much as a fungus would do. The 

 most remarkable case, however, is Buxbaumia, where the 

 leaves are almost completely absent and the saprophytic habit 

 very strongly pronounced. Most of the Mosses, however, are 

 abundantly provided with assimilative tissue, and grow upon 

 almost every substratum, although most of them are pretty 

 constant in their habitat. A number of species are typically 

 aquatic, e. g., Fontinalis and many species of Sphagnum and 



160 



