PEBONOSPO RE^. 



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 hyphse ; those 

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



Fig. 178. — Tlie sexual organs and fertilization of Pei'onospora Atsinearum. 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 oosphere. 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, Pig. 178). 

 The other branches, the young anthe- 

 ridia, which arise upon the same fila- 

 ments as the oogonia and near to 

 them, or apon 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 

 from the rest of the filament by a 

 transverse partition in each case (a, 

 Fig. 178). At this stage the an- 

 theridia become applied to the oogonia, and in each of 

 the latter the protoplasm has still further condensed and 



* Consult De Bary's " Morphologie und Pbysiolofrie der Pilze," etc., 

 pp. 158-159, a translfttion of wbicli appeared in " Qrevillea," 1873, p, 

 150, 



Fig 179.— Oogonium of Pe- 

 rono'-pora, with, its contained 

 oosphere; at the left is the 

 antheridinm, which has pene- 

 trated the ooeoniuiu and 

 brought its fertilizing tube - 

 into contact with the oo- 

 sphere. Much magnified.— 

 After De Bary. 



