224 



ALG.E 



as the rest, lying either singly among the ordinary vegetative cells, or 

 sometimes in groups of as many as twelve. In most species each 

 antheridial cell divides either horizontally or vertically into two ' special 

 mother-cells," each of which gives birth to an antherozoid. The oogones 

 are developed either in the same filament as the antherids or not, some 

 species being monoecious, others dicecious. They are also frequently in 

 groups of from three to six. Their development always takes place out of 



11. 



Fig. 20I.— I. A, filament of (Edogonumi ciliat^iui Hass. '; 

 «, zoosporange ; og, oogone with 'dwarf male,' in. B, oogone 

 at the moment of impregnation ; o, oosphere ; z, antherozoid ; 

 in, 'dwarf male.' C, C£".^t';;^^///^^r?<w Hass. ; piece of filament 

 in which zoospores, z, are being formed, from which the 'dwarf 

 males ' are produced (x 250). II. Zoospores ; A, still within 

 the zoosporange ; ^, in the act of escaping ; C, free zoospore. 

 (After Pringsheim.) 



the upper half of the lower portion of a cell provided with cell-caps at 

 its upper end, which has just divided, and which, directly after the 

 division, swells up into a spherical or ovoid form. Immediately before 

 impregnation the protoplasm contracts into an oosphe7'e, containing in 

 one portion densely crowded chlorophyll-grains, and, at the spot opposite 

 to the part of the wall of the oogone which is to open, a hyaline 'receptive 

 spot.' The oogone opens in several ways. Sometimes an oval orifice i.s 



