DEVELOPMENT OF PLANTS 



185 



The male and female gametes are produced in gametangia that 

 are formed from short branches. The males are developed in 

 large numbers in curved branches that become cut off from the 

 filament by a cross wall (Fig. 114, A) and the gametes finally 

 escape through an opening that forms at the apex of the branch. 

 A gametangium that produces clearly differentiated male gametes 

 is called an antheridium (plu. antheridia) and the gametes are 

 frequently called antherozoids or sperms. A single female 

 gamete is found in a similar branch which becomes rather egg- 

 shaped and at maturity opens at the beaked end (Fig. 114, B). 

 A single-celled female gametangium is called an oogonium and 

 the female gamete is frequently referred to as the oosphere or 

 egg. The male gametes are discharged a few minutes after the 



Fig. 114. Sexual reproduction of Vaucheria: A, portion of a filament that 

 has formed two branches which have grown into a male, aw, and female, og, 

 gametangia. B, later stage, the gametangia have opened, permitting the 

 escape of the male gametes and the fertilization of female gamete. C, gam- 

 etospore detached from the filament. 



oogonium opens, when they swarih about the open end of the 

 female gametangium and readily enter it. As soon as fusion has 

 been effected the gametospore becomes invested with a thick wall 

 and in this condition can endure a limited drought. In germi- 

 nating it develops directly into a new plant. This feature of the 

 life history of Vaucheria is therefore of a more primitive nature 

 than in the case of Ulothrix. In the following studies you will 



