CHAPTER XVI. 



OOSPOEE^. 



321. — The distinguishing feature of the plants belonging 

 to this division is that they develop a large cell (the oogo- 

 nium), differing from those about it in size and general ap- 

 pearance, which contains one or more rounded masses of 

 protoplasm (the oospheres), which are subsequently fertilized 

 by the contents of a second kind of special cell of much 

 smaller size (the aniheridium). The oogonium is the fe- 

 male reproductive organ, and the autheridium the male. 

 The protoplasm of the latter is in some cases transferred by 

 direct contact to the oosphere ; in other cases it is first broken 

 up into motile bodies, the spermatozoids, which then come 

 to and become fused with the oosphere. The oosphere itself 

 is never motile, and in most cases it remains within the 

 parent plant until long after it is fertilized. The result of 

 fertilization is the production of an oospore, which differs 

 from the oosphere structurally in having a hard and gener- 

 ally colored coating, and physiologically in having the power 

 of germination and growth after a period of rest of greater 

 or less duration. 



322. — The plants of this division vary greatly as to the 

 development of the plant-body. In some cases it is a feebly 

 united colony {Volvox and its allies), while in its highest 

 forms it is a well-developed thallus, with even the beginning 

 of a differentiation into Caulome, Phyllome, and Koot 

 {FucacecB). 



§ I. "Volvox akd its Alues. 



323. — In the classification of the plants of this division 

 the lowest place must be assigned to Volvox and Eudorina, 

 which, as previously stated, are, with doubtful propriety, 



