1 86 MOSSES AND FERNS chap. 



belongs to the same segment as the leaf standing above it, and 

 therefore is not axillary in its origin. The mother cell of the 

 young branch projects above the surrounding cells, and in it 

 are formed in succession three oblique intersecting walls which 

 enclose the narrow pyramidal apical cell (Figs. 86, 87). The 

 secondary divisions in the first set of segments are not so 

 regular as in the later ones, but the bud rapidly grows, and 

 very soon the perfectly regular divisions of the young segments 

 are established. So far as investigations have been made upon 

 other genera, they follow the same line of development as 

 Ainblystegium, Fontinalis, and Sphagnum. 



Where the growth of the main axis is stopped by the 

 formation of sexual organs, a lateral branch frequently grows 

 out beyond the apex of the main axis, as in Sphagnum, and 

 thus sympodia arise. In other cases, where the growth of the 

 lateral branches is limited, characteristic branch systems arise, 

 such as we find in TJiuidium or Cliniacium (Fig. 75). 



Compared with Aniblystegium, the growing point of Ftmaria 

 and other Mosses of similar habit is much broader, and the 

 apical cell not so deep. The arrangement of the segments is 

 much the same, except that the original three-ranked arrange- 

 ment of the segments which is retained in Fontinalis ^ is replaced 

 in most Mosses by a larger divergence, owing to a displacement 

 like that in Sphagnum. 



A cross-section of the older stem (Fig. 88, D) shows in 

 most Bryineae a central cylinder of small thin - walled cells 

 surrounded by a large-celled cortical tissue, which in the older 

 parts of the stem often has its walls strongly thickened and 

 reddish brown in colour. An epidermis, clearly recognisable 

 as such, cannot usually be detected. The outer cells contain 

 chlorophyll, which is wanting in the central cylinder. 



The rhizoids in Funaria grow mainly from the base of the 

 stem, and the first ones arise very soon after the young bud is 

 formed. Their growth, like that of the protonemal branches, 

 is strictly apical, and they branch extensively. The young 

 ends are colourless, but as they grow older the walls assume a 

 deep brown colour. Usually the division walls in the rhizoids 

 are strongly oblique. Their contents include more or less oil, 

 and where they are exposed to the light, chlorophyll. 



^ This is only strictly true in the smaller branches. 



