CONFERVOIDE& HETEROGAM^E 



221 



opens at its apex and exudes a drop of colourless mucilage. The oogone 

 still contains chlorophyll, and its protoplasmic contents contract into a 

 green oosphere. At the same time flask-shaped protuberances grow out 

 from adjoining cells, and these, becoming cut off from the parent- 

 cells by septa, are the antherids. The entire contents of each antherid 

 escape as a single ovoid antherozoid furnished with two very long and 

 slender cilia. Other species are dioecious, the antherids being produced 

 on different individuals from the oogones. The antherozoids probably 

 pass into the trichogyne through its open apex, and thence into the oogone; 

 but the act of impregnation has not actually been observed hitherto. 

 The first result of the impregnation of the oosphere is its investment 



FIG. 199. ColeochcetepulvinataK. Br. A, portion of fertile thallus(x 350); an, antherid ;og, oogone ; 

 h, hyaline hair ; z, antherozoid. J3, ripe oogone with its pericarp, r ( x 280). C, formation of" 

 carpospores within the spermocarp ( x 280). D, zoospores ( x 280).' (After Pringsheim.) 



by a cell-wall of cellulose, and a considerable increase in its size. The 

 fertilised oogone, with the exception of the trichogyne, then becomes 

 surrounded by & pericarp, or cortical layer of cells ; the oogone and peri- 

 carp together constitute the spermocarp enclosing the fertilised oosphere 

 or oosperm. The spermocarp subsequently becomes further invested by 

 a cortex of closely applied branches resulting from the continued de- 

 velopment of cells at the base of the spermocarp. After the complete 

 development of this organ, which takes place between May and July, 

 the vegetative cells of the thallus disappear, and its walls assume a dark- 

 brown colour. The spermocarp remains dormant through the winter :. 



