92 MOSSES AND LIVERWORTS 



or recurved (fig. 25), etc. In some the midrib, 

 or nerve, as it is called (and observe that there are 

 never any branching ribs or veins in a moss leaf, 

 as in most ordinary leaves, only the one central 

 nerve), reaches the whole way up the blade or 

 lamina of the leaf (figs. 19 and 22) ; in others it is 

 even extended beyond the end of the leaf (when 

 it is said to be excurrent) (fig. 16), or this 

 extension may take the form of a long, trans- 

 parent hair-point (figs. 3 and 25). In others, 

 again, it ceases before reaching the end of the 

 leaf (figs. 14 and 18). In some cases it is forked 

 or double (figs. 7, 8, and 12) ; while sometimes it 

 is absent altogether (figs. 4 and 5). Some mosses, 

 moreover, produce very different forms of leaf on 

 the same plant; for instance, the leaf drawn at 

 Plate IV. fig. 15 was taken from the stem of 

 the Common Rough-stalked Feather-moss (Brachy- 

 thecium rutabulum), a well-known moss, with 

 bright, sheeny green leaves, that grows freely on 

 banks, walls, tree-roots, etc., and produces an 

 abundance of pretty, red, egg-shaped capsules in 

 the winter ; fig. 16 gives the form of leaf peculiar 

 to the branches of the same moss ; while at fig. 17 

 we have one of the special leaves which surround 

 the base of the fruit-stalk (known as the peri- 

 chostial leaves), which, it will be seen, has a 

 distinctly different shape from either of the other 

 two. Occasionally the leaves that spring from 

 the lower portion of the stem vary considerably 



