224 



ALG.E 



as the rest, Ipng 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 dioecious. They are also frequently in 

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



II. 



Fig. 20I.— I. A^ filament of CEAigoniMm cfliattem Hass.^ 

 K, zocspoiange ; a^j oogone with * dwarf male,* m. S, ot^Dne 

 at the moment of impiegnation ; Oj oosphere ; s, antherozoid^ 

 m, *(fwaif male.' C,<£.^e»iefl^^ajvnrHa£S.;iueceoffiIameiit 

 in which zoospores, s, ate being formed, from which Che 'dwtizf 

 males ' are produced (x 250X 11. Zoospores ; ^, still withia 

 the zoc^porange ;^4.in the act of escaping ; C, &ee zoospore, 

 (.^ter I^ingshdm.) 



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 

 di^sion, swells up into a spherical or ovoid form. Immediately before 

 impregnation the protoplasm contracts into an oosphere, 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 is 



