THE 



233 



Zodsporangia 



Zoospore 



Life history. The life history of Vaucheria thus presents 

 a marked contrast to that of Spirogyra or Protococcus. Its 

 gametangia are unlike and are 

 often for this reason termed the an- 

 theridium, or male gametangium, 

 and the oogonium, or female 

 gametangium. 



The female gamete is a large, 

 stationary cell abundantly stored 

 with nutriment for the produc- 

 tion of a new gamete plant. The 

 male gametes are small and ac- 

 tively motile, and are 

 produced in great num- ^^^ Old zoospore 

 bers to insure fertiliza- 

 tion of the nonmotile 

 egg. The gamete plant 

 results from the ger- 

 mination of the zygote 

 produced by the union 

 of the male and female 

 gametes. 



Asexual reproduction 

 is also provided for by 

 highly specialized motile asexual bodies called zoospores. The 

 life history of Vaucheria, therefore, presents the same stages of 

 sexual and asexual reproduction as Chlamydomonas. 



''Holdfasts 



FIG. 122. Asexual reproduction in Vaucheria 



a, b, formation and expulsion of the zoospore c ; 

 <7, early germination of the zoospore; e, new fila- 

 ment formed. , b, and c, after Strasburger; d and 

 e, after Sachs 



(EDOGONIUM 



(Edogonium is one of the highest types of the filamentary 

 algse, in which the filaments are composed of many cells. The 

 general facts regarding its life history are similar to those of 

 Vaucheria in that it reproduces by both the sexual and the 

 asexual method. The female gametangium is called an oogo- 

 nium and the male gametangium an antheridium, as in Vaucheria. 

 Both organs arise from ordinary cells of the filament. 



