66 



MOSSES AND FERNS 



CHAP. 



briaria especially is very much developed, and projects far 

 beyond the ripe capsule ( Fig. 21). 



The germination of the spores corresponds in the main with 

 that of Riccia. Except in cases where the exospore is very 

 thin, in which case it is not ruptured regularly, the exospore 

 either splits along the line of the three converging ridges upon 



D 



FIG. 27. Targionia Jiypophylla. Germination of the spores, X about 200. In B two 

 germ tubes have been formed; C and E are optical sections; x, apical cell; r, 

 primary rhizoid; sp, spore membrane. 



the ventral surface, and through this split the endospore pro- 

 trudes in the form of a papilla, as in Riccia; or in Targionia 

 (Fig. 27) the exospore is usually ruptured in two places on 

 opposite sides of the spore, and through each of these a filament 

 protrudes, one thicker and containing chlorophyll, the other 

 more slender and nearly colourless. The first is the germ tube, 

 the second the first rhizoid. In Fimbriaria California the 

 first rhizoid usually does not form until a later period. In 

 Targionia a curious modification of the ordinary process is 

 quite often met with (Fig. 27, B). Here, by a vertical divi- 

 sion in the very young germ tube, it is divided into two similar 

 cells, Which both grow out into germ tubes. Whether 

 both of these ever produce perfect plants was not determined, 

 but the first divisions in both were perfectly normal. The 

 first divisions in the germ tube are not quite so uniform as in 



