422 



BOTANY OF THE LIVING PLANT 



through the air. But it shows its real nature on germination by pro- 

 ducing zoospores which arc liberated in water. The modification of 



FIG. 357- 



Fertilisation of the Peronosporeae. i. Peronospora parasilica, young multi- 

 nucleate oogonium (og), and antheridium (an). 2. Albugo Candida. Oogonium with 

 the central, unt-nucleate egg (os), and the fertilising tube (a) of the antheridium which 

 . introduces the male nucleus. 3. The same. > The fertilised egg (o) surrounded by 

 periplasm (p). (After Wager, x 666.) (From Strasburger.) 



such an antheridium as is seen in Vaucheria into the pollinodium of the 

 Peronosporeae, is a comparatively slight one: the latter does not liberate 



FIG. 358. 



Monoblfpharis sphatrica. End of a filament with terminal oogonium (o) and an 

 antheridium (a), i, before formation of the gametes. 2, spermatozoids (s) escaping 

 and approaching the opening of the oogonium. 3, osp, ripe zygote and an 

 empty antheridium. (After Cornu. x 800.) (From Strasburger.) 



