43 



CHAPTER XI. 



SYSTEMATIC ARRANGEMENT OE MOSSES. 



The main divisions of Mosses depend upon the situation of 

 the fruit, its nature, and the mode of branching ; but, as in 

 other branches of natural history, it is impossible in any 

 natural arrangement to frame characters which shall be free 

 from exceptions. They are divided by authors according to 

 these principles into five groups. 



1. Pleurocarpi. Fruit lateral, springing immediately from 

 the stem. 



2. Cladocarpi. Fruit terminal, on short lateral branches. 



3. Acrocarpi. Fruit terminal. 



4. Schistocarpi. Fruit splitting longitudinally into four or 

 more valves, adhering above. 



5. Syncladei. Branches fasciculate. 



Of these the second is not strictly natural, and the character 

 is difficult of application, as Acrocarpous and Cladocarpous 

 species occur in the same genus. 



It has been proposed moreover to divide the first three 

 groups into Stegocarpi and Cleistocarpi, the former comprising 

 those in which the spores escape on the separation of the lid, 

 the latter, as in Phascum, by the decay or irregular rupture 

 of the sporangium; but as it is probable that in a really 



