234 PHARMACEUTICAL BOTANY 



small, sterile, vegetative cells that do not divide and from 10 to 12 

 larger vegetative ones that divide to form new colonies. The latter 

 slip inward below the level of the smaller cells and through repeated 

 divisions form a number of ciliated cells jointed by cytoplasmic 

 threads, which in reality is a minature colony. This then escapes to 

 the exterior through the rupturing of the gelatinous wall of the old 

 colony. 



During autumn of the year, certain of the ordinary cells undergo 

 differentiation, some to form sperm cells, others, egg-cells. When 

 about three times the size of the ordinary sterile cells, the sperm cells 

 divide repeatedly to form a cluster of elongated secondary cells 

 [Fig. 112 (ia, a 2 and 5),] each of which contains an orange colored 

 endochrome with a red corpuscle and an elongated beak, bearing a 

 pair of flagella (lash-like processes). The cluster in time separates 

 into motile antherozoids [Fig. 112 (6, 7)] which finally escape into 

 the cavity of the volvox sphere through rupture of the investing 

 wall. The flask-shaped egg cells (ib, b) increase greatly in size with- 

 out dividing. Each shows vacuoles, then becomes filled with a 

 dark green pigment, becomes spherical and acquires a gelatinous 

 envelope. It then passes into the cavity of the sphere where it is 

 surrounded by numerous antherozoids (3) and is finally fertilized. 



The product of this fertilization is an oospore (4) which ere long 

 becomes covered with an internal smooth membrane and a thicker 

 external spinose coat. The chlorophyll within then disappears and 

 starch and a reddish- or orange-colored oil make their appearance. 

 Up to 40 of these oospores have been observed in a single volvox 

 sphere. Not long after the formation of these oospores the whole 

 parent colony breaks up and the oospores fall to the bottom of the 

 pool to pass the winter season. As early as February each oospore 

 germinates to form another volvox colony, which repeats the life 

 cycle described. 



3. Order Confervales. In this order are included a variety of 

 green filamentous and membranous forms some of which show sexual 

 reproduction. 



Family Ulothricaceae. Ulothrix zonata, a typical representative 

 of this family, is a filamentous organism found growing on stones 

 around ponds, on rocks along the shores of lakes, in slow-moving 



