138 PLANT-LIFE 



gation. It is worthy of note that protonema may be 

 developed from various parts of a plant, as well as from 

 spores; they are known to rise from leaves, stems, 

 rhizoids, and fruits. Vegetative buds are thrown off by 

 a number of Mosses. The alternation of generations in 

 Mosses may be thus stated : 



Sexual. Asexual. 



Spore Embryo 



Protonema Sporogonium | ^ a , 



Moss-plants Spore 



/ \ 



Antheridia Archegonia 



\ / 



Embryo 



The Mosses are divided as a rule into four Natural 

 Orders the Sphagnacece, Andreceacece, Phascacece, and 

 Bryacece ; there are good reasons for including the 

 Pkascacece in the Bryacece. In regard to species, the 

 Mosses far outnumber the Liverworts. 



Sphagnacece. The Bog Mosses, which grow on swampy 

 ground, covering large tracts, and in some districts form- 

 ing extensive and dangerous bogs. The bogs of Ireland, 

 composed mainly of Bog Mosses, occupy many thousands 

 of acres. The Order has but one genus, Sphagnum ; 

 this embraces a goodly number of species. All the 

 Sphagnums have a remarkable capacity for absorbing 

 and holding water, and it is for this reason that they 

 are commonly drawn into the service of the horti- 

 culturalist. The remains of Sphagnum enter into the 

 composition of peat. The colour varies; it is usually 

 pale green, but may be yellow or almost red. The plants 



