PERONOSPOREM. 



261 



346 In the sexual reproduction,* which, as above stated, 



always takes place in the intercellular spaces of the host, 

 lateral branches of two kinds arise upon the hyphae ; those 

 of the one kind, the young oogonia, become greatly thickened 



Fig. 178. — The sexual organs and fertilization of Peivrtospora AMnearum. a, 

 youngest stage ; o, young oogonium ; n, young antheridinm ; &, the pame somewhat 

 later ; the antheridinm is beginning to thrust its heak-like process (fertilizing tube) 

 into the oogonium ; e, the same at a still later stage— the fertilizing tube has reached 

 the oosphete. x 350.— Alter DeBary. 



in diameter, and finally assume a globular shape ; their 

 highly granular protoplasm becomes condensed, and finally 

 separated from that of the remainder of the filament by a 

 transverse septum at the base of each oogonium {a, Kg. 178). 

 The other branches, the young anthe- 

 ridia, which arise upon the same fila- 

 ments as the oogonia and near to 

 them, or upon other filaments which 

 are in proximity to the oogonia-bear- 

 ing ones, become elongated and club- 

 shaped ; their protoplasm (also gran- 

 ular) becomes condensed in their up- 

 per portions, which are soon separated 



Fig 179.— Ongnnium of Pe- 

 roiw^pora, with its contained 

 ooSphere; at the left is the 

 antheridium, which has pene- 



from the rest of the filament by a '^.f^^^.X fe?Fmi."ng tu"e 



into contact with the oo- 

 sphere. Much magnified.— 

 After De Bary. 



transverse partition in each case (a. 



Pig. 178). At this stage the an- 



theridia become applied to tlie oogonia, and in each of 



the latter the protoplasm has still further condensed and 



* Consult De Bary's " Morpliolooie und Physiolojrie der Pilze," etc., 

 pp. 158-159, a translation of wliicli appeared in " Grevillea/' 1873, p. 

 150. 



