194 MOSSES AND FERNS chap. 



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 oblicjue intersecting walls which enclose the 

 narrow pyramidal apical cell (Figs. 98, 99). 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 estab- 

 lished. So far as investigations have been made upon other 

 genera, they follow the same line of development as Ambly- 

 stegium, Fontinalis, and Sphagnum. 



Where the growth of the main axis is stopped by the form- 

 ation 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 lat- 

 eral branches is limited, characteristic branch systems arise, 

 such as we find in Thuidiiim or Climacium (Fig. 86). 



Compared with Amblystegium, the growing point of 

 Fiuiaria 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 arrangement of the segments which is retained in Fonti- 

 nalis^ 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. 100, D), shows in 

 most Bryales a central cylinder of small thin-walled cells sur- 

 rounded 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 ones 

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

 brown colour. Usually the division walls in the rhizoids are 

 vStrongly 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. 



