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A TEXTBOOK OF THEORETICAL BOTANY 



Epiphragm 



Peristome 



Fig. 426. — Polytrichunt commune. Apical 

 view of sporogoniuni after removal 

 of the operculum. 



B 



Fig. 427. — Polytrichiim commune. Protonema. A, Cable-like strands of 

 filaments in an old protonema. B, Buds destined to form leafy branches 

 forming on a protonema. {After Schimper.) 



Sphagnales 



The order Sphagnales is monotypic, that is to say, it contains only a 

 single genus, Sphagnum, which has, however, hundreds of species. They 

 are among the largest Mosses in point of size, as well as among the most 

 widely distributed, occurring in all parts of the world except the Arctic 

 regions. Unlike most other Bryophyta they are markedly social, growing in 

 extensive masses on boggy and peaty soils, where they often form the greater 

 part of the plant covering. They contribute so importantly to the building 

 up of certain types of wet peat that the term " sphagnum bog " is a recognized 



