THE BRYOPHYTA : MUSCI, THE MOSSES 439 



descriptive term in Ecology. They may also grow as submerged aquatics 

 in peaty pools. 



Although undoubtedly INIosses, they stand so far apart from the others 

 in structure that they have been classed as a distinct group by some writers. 

 In their vegetative structure they are unique, but in the spore capsule they 

 show certain points of resemblance to Anthoceros, which in most other 

 respects seems to be remote from them. Lacking any knowledge of their 

 geological history, we must leave the question of their nearest relationships 

 in abeyance. At the present day the chief centre of distribution of the genus 

 is in Brazil, and it probably only reached Europe in recent times, i.e., about 

 the beginning of the glacial period. 



Sphagnum 



It is unnecessary in this case to cite particular species types because 

 they differ from one another on such small and often obscure points that a 

 general description will serve for almost any species which mav be examined 

 (Fig. 428). 



Fig. 428. — Sphagnum sp. Fertile plant with sporogonia. 

 Slightly reduced. 



Vegetative Structure 



The germination of the spore produces a protonema, which is thalloid 

 and lobed, not unlike a young plant of a Liverwort or a prothallus ot 

 Equisetum (Fig. 429). In poor light, however, the protonema may develop 

 into filaments as in other Mosses, and the transformation into the thalloid 

 form depends on the light intensity. Separated parts of the mature plant 

 can either develop secondary protonema, though the power to do this is 

 apparently restricted to the short apical shoots, or they may develop new 

 leafy shoots directly from single cells, thus affording an excellent means ot 

 vegetative propagation (Fig. 430). 



