396 



BOTANY OF THE LIVING PLANT 



(Fig. 334). In structure the zoospore shows the cilia in pairs, each 

 pair related to a nucleus which is superficial, while the chloroplasts 

 lie within. The origin and structure of the zoospore suggests that 



FIG. 334. 



Vaucheria sessilis. A.= young sporangium. B = zoospore, with the sporangium 

 from which it has escaped. C a portion of the peripheral zone of a zoospore. 

 D = a young plant, with rhizoids, developed from a zoospore. (A, B, after Gotz ; 

 D after Sachs ; C after Strasburger.) (From Strasburger.) 



it represents the undivided contents of a whole sporangium, such as 

 may be seen in other Siphonales. 



The Siphonales and Siphonocladiales reproduce sexually : but 

 degrees of difference in size of the gametes are seen. The differentia- 

 tion thus indicated must be held as distinct from, though parallel 

 with that already described in the Brown Algae, and in the Ulothri- 

 cales. In Acetabularia the gametes are of equal size, and those 

 produced from different sporangia, or from different plants fuse in 



