PERONOSPORE^. 



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 Peronospora Alsinearum. a, 

 youngest stage ; o, young oogonium ; n, young antheridium ; b, the same somewhat 

 later ; the antheridium is beginning to thrust its beak-like process (fertilizing tube) 

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

 the oosphete. X 350. Alter De Bary. 



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, Fig. 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. Oogonium of Pe- 

 rono>-pora, with its contained 



frnm tVip rpf nf flip filampnf Vw n trnted the oosronium and 



L brought its fertilizing tube 



transverse partition in each case (a, int <> contact with the oo- 



v ' sphere Much magnified.' 



Fig. 178). At this stage the an- After DC Bary. 



theridia become applied to the oogonia, and in each of 



the latter the protoplasm has still further condensed and 



* Consult De Bary's " Morphologic und Physiologic der Pilze," etc., 

 pp. 158-159, a translation of which appeared in " Qrevillea," 1873, p 

 150. 



