198 THE ALG^E 



developed singly in terminal cells (sporangia), which are cut off 

 at the ends of the filaments by the formation of a cross wall 

 (Fig. 189, A). The protoplasm in the sporangium contains 

 hundreds of nuclei from the beginning, and pairs of cilia are 

 formed all over the surface of the protoplast opposite them 



FIG. 189. Asexual reproduction of the green felt (Vaucheria) 



A, formation and discharge of the large, many-ciliate zoospore from the terminal 

 sporangium ; B, the zoospore showing the ciliated surface ; C, section through 

 the surface of the zoospore showing the pairs of cilia above the nuclei and 

 the layer of plastids beneath ; D, germination of zoospore ; E, young plant of 

 Vaucheria, the two filaments having arisen at opposite ends of the zoospore, 

 one having developed an organ of attachment or holdfast h ; F, a group of 

 plastids, the lower in process of division. A, B, after Gotz; C, after Stras- 

 burger ; D, E, after Sachs 



(Fig. 189, C). The entire mass of protoplasm then slips out 

 from the end of the sporangium (Fig. 189, B} and swims slowly 

 away, but soon comes to rest and puts forth one or more fila- 

 ments (Fig. 189, D). The nuclei and pairs of cilia in this inter- 

 esting zoospore of Vaucheria unquestionably represent the two- 

 ciliate zoospores characteristic of most of the Siphonales and 

 the green algae in general. The protoplasmic divisions neces- 

 sary to cut out the numerous zoospores in a sporangium are 



