14 HANDBOOK OF BRITISH MOSSKS. 



branching in each tuft, when torn to pieces, appears dichoto- 

 mous throughout, each fork representing a year's growth. 

 Thus a tuft of Moss may be entirely dead below, though still 

 fixed by the rootlets, while the circumference is perfectly green 

 and luxuriant. In Pleurocarpous Mosses, on the contrary, 

 true ramification constantly takes place, and the fruit is in 

 fact terminal on a very short branch, whose leaves differ con- 

 siderably from those of the main stem or branches. In Cla- 

 docarpous Mosses the branch (p. 4) is merely a little more 

 developed. 



The branches are sometimes irregularly disposed, sometimes 

 decidedly pinnate or bipinnate, and sometimes fasciculate. 

 The stem is occasionally quite unbranched below, as in Clima- 

 cium dendroides (Plate 13, fig. 2) or Thamnium alopecurum 

 (Plate 13, fig. 1), and the branches collected above, in which 

 case they are called ' dendroid,' from the resemblance of the 

 whole to little trees. 



The stem is in general cylindrical, but it is sometimes flat- 

 tened or depressed, and in some cases is distinctly triquetrous. 



d. — The stem and branches are partially or completely 

 clothed with leaves, which are sometimes few and scattered 

 below, though densely crowded above. In some cases, as in 

 Buxbaumia (Plate 19, fig. 6) and Tetrodontium (Plate 19, 

 fig. 7), they are more or less rudimentary, but such exceptions 

 are not of frequent occurrence. 



They vary somewhat in structure. Sometimes they consist 

 of a single stratum of cells, which usually contain chlorophyll 

 throughout the whole lamina, but more frequently there is 

 either a thickening at the base, which breaks up at times 

 into two or three nerve-like divergent threads, or there is one 

 central nerve of variable length and thickness, occasionally 

 projecting far beyond the tip of the leaf, and forming a hair- 

 like point. 



