292 



Ulotrichales 



of the cells is not unlike that in the genus Geminella, their frequent dis- 

 position in pairs resulting from the simultaneous division of many cells. 

 Each cell possesses a massive parietal chloroplast, often with most obscure 

 limitations, and generally furnished with one pyrenoid. Numerous small 

 grains of starch can as a rule be detected in the healthy cell. 



Asexual reproduction takes place by zoogonidia which arise singly, or in 

 twos or fours, from any cell of the filament. The zoogonidium is ovoid or 

 ellipsoid in form, biciliated, and provided with a pigment spot and two 

 contractile vacuoles. 



Fig. 187. A D, Cylindrocapsa involuta Eeinsch, x 480 (after Cienkowski). E and F, 

 C. conferta W. West, x 520. a, antheridium ; an, antherozoid ; oo, oogonium. 



Sexual reproduction of a comparatively high type was observed in 

 Cylindrocapsa involuta by Cienkowski ('76). The gametes are well dif- 

 ferentiated antherozoids and eggs. The antheridia result from the active 

 division of some of the vegetative cells, and they finally consist of one, two 

 or four longitudinal series of small rounded cells (fig. 187-4 a). Each 



