THE ARCHEGONIAT^ 



225 



like that of the simple Hepaticae. The protoneina arises primarily 

 from the germination of the spore, but may develop secondarily from 

 various parts of the gametophyte, or even, in exceptional cases, from 

 the sporophyte. From the protonema special branches arise, which 

 become the leafy shoots, or gametophores, upon which the sexual 

 organs are borne. 



The growth of the filamentous protonema is apical, and the divi- 

 sion walls are often strongly oblique, this being especially the case in 

 the branches which penetrate the earth and assume the character of 

 rhizoids. These branches lose the chlorophyll, and their cell-walls 



FIG. 187. Funaria hygrometrica. A, fragment of a protonemal filament, with 

 young bud developing from it. B, the same bud in optical section. C, an older 

 bud, l,from the surface; 2, in optical section; x, apical cell (X 225). D, proto- 

 nemal filaments with an older bud, gam, attached (x 36). 



become thick and brown in color. In Sphagnum the protonema 

 is a flat thallus, which in its earlier stages often shows a two-sided 

 apical cell, like that in the lower Hepaticse. From the margin of this 

 thallus, filaments like those of the typical moss-protonema may be 

 formed. It is probable that the thalloid protonema of Sphagnum is 

 an older type than the filamentous one of the typical Mosses. 



Gametophore. The leafy shoot begins as a lateral branch of the 



protonema (Fig. 187). The bud enlarges slightly, and there are 



formed, in rapid succession, three intersecting walls, which cut out a 



tetrahedral apical cell, from which are then cut off three series of 



Q 



