72 



A TEXTBOOK OF THEORETICAL BOTANY 



Fig. 54. — Volvox aureus. Mature oospores with 

 spiny walls. 



advanced type, with well-developed 

 oogamy. The gametes may be pro- 

 duced either in distinct colonies or 

 in the same one, either simultane- 

 ously or, more often, at different 

 times. The antherozoids are biflag- 

 ellate and fusiform, i.e., spindle- 

 shaped (Fig. 51). They have pale 

 yellowish-green chloroplasts, and are 

 developed in plates or circular masses 

 (Fig. 52) formed by the division of 

 the contents of specially enlarged 

 cells. The female gametes or 00s- 

 pheres are rounded or flask-shaped 

 and have no flagella (Fig. 53). They 

 are contained in much enlarged cells of 

 the colony, which are like the gonidia 

 but larger. The oosphere often de- 

 velops a kind of protrusion or beak, 

 which is probably the point of entry 

 of the antherozoid. After fertiliza- 

 tion a spherical oospore is formed, 



the interior of the parent 

 sphere, and collectively may 

 nearly fill it. They are 

 eventually liberated by the 

 breaking up of the parent 

 colony (Figs. 48 and 49). 



As these daughter col- 

 onies develop, the anterior 

 or outer ends of the cells are 

 directed inwards towards 

 their respective centres. 

 Shortly before their cells de- 

 velop flagella the daughter 

 colonies turn themselves 

 completely inside out by a 

 folding process which begins 

 from the inner end, and thus 

 restores the correct orienta- 

 tion of the cells (Fig. 50). 



Sexual reproduction is of 



-Gonidium 



>Volvox colony. 



AntherldiuTi 



•Oogonla 



Oospore 



Anthero2oides 



Fig. 55. — Life-cycle of Volvox. 



