DEVELOPMENT. 



Bryum (fig. i, 4), etc. The cells at the base of the leaf 

 are frequently of different form from those of the upper part 

 of the leaf, and are often colourless and transparent. 



The centre of the leaf is often occupied by elongated 



FIG. 5. Hvpnnm rutaluluw. i, a plant natural size, showing pleurocarp ous 

 inflorescence. 2, fruit magnified, showing 2 a, conical operculum ; 2 b, rough seta, or 

 fruit-stalk ; 2 c, recurved perichsetial leaves. 3, fringe, or peristome ; a, inner 

 peristome ; b, outer peristome. 4, stem leaf ; 4 a, cells of leaf highly magnified. 



cells, forming what is called the nerve or midrib (fig. 5, 4). 

 This nerve is usually simple, but may be forked, as in 

 Isotkecium mynrum ; or there may be two nerves, as in 

 Hypnum triquetrum, common on marly banks ; or the leaves 



