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 ofi by 

 a number of Mosses. The alternation of generations in 

 Mosses may be thus stated : 



Sexual. Asexual. 



Spore Embryo 



/Seta 



Protonema Sporogonium (c^p.^i^ 



Moss-plants Spore 



Antheridia Archegonia 



\ / 



Embryo 



The Mosses are divided as a rule into four Natural 

 Orders — the SphagnacecB, Andreceacece, Phascacece, and 

 BryacecB ; there are good reasons for including the 

 PJiascacecB in the Bryacem. In regard to species, the 

 Mosses far outnumber the Liverworts. 



SphagnacecB. — 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 



