BRAITHWAITE : THE STUDY OF MOSSES, 



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M;i/um, Jhynm, and Hypmim, the capsule is usually drooping, 

 and when the peristome is closed by moisture, the spores must 

 await a drier interval for dispersion. 



The columella is the central pillar of the capsule continued 

 from the central cells of the seta to the tissue of the lid. 



In many mosses, when the lid comes off no trace of a 

 peristome is to be seen, and they are said to be gymnostomous, 

 and when genera of mosses were founded on the number of 

 teeth in the peristome, all those in which the peristome was 

 absent were lumped togetlier in one genus Gymnosfomum^ 

 although differing widely in habit and leaf-structure. We now 

 regard these as the lowest forms of such peristomate genera as 

 they agree with in general structure. Taking these highest forms 

 we find the first parts to be lost are the cilia, and then all the endos- 

 tome, next the inner layer of cells in the teeth of peristome, which 

 thus become rigid and imperfect, these also disappear, and the 

 capsule is gymnostomous, and last of all, it cannot even produce 

 a decent lid. Such is a brief outline of the structure oi the true 

 mosses, and I may deal with the other two groups by just 

 indicating the chief points in which they differ from them. 



The Sphagna or Peat-mosses comprise probably a liundred 

 closely allied plants, possessing a very uniform aspect, differing 

 considerably from that of the Bryince, and inhabiting almost 

 exclusively moorland bogs, in which they form great spongy 

 masses, and are also independent of roots. 



The stem has a distinct pith, the external layers are 

 mdurated, and generally coloured brown or red, and coated by 

 a loose cuticle of empty vesicular cells in one to four strata, 



