154 BOTANY. 



(species of Albugo) the conidia-bearing branches collect 



FiG.81.— Slio-wmgtips of two conidiophores of Potato-mildew (Phytoph- 

 thora infestans). Highly magnified. 



under the epidermis and rupture it. 

 Here the conidia are borne in chains or 

 bead-like rows (Fig. 82). 



274. In some species the conidia germi- 

 nate by forming a tube ; in others they 

 divide internally and finally emit many 

 zoospores. The latter eventually pro- 

 trude a tube and bore their way into the 

 cells of the host (Fig. 83, a to i). 



275. The sexual reproduction always 

 takes place in the intercellular spaces of 

 the host. Lateral branches of two kinds 

 appear upon the hyphse; those of one 

 kind. (the young oogones) become greatly 

 thickened and finally assume a globular shape (Fig. 84, o) ; 

 the other branches (the young antherids) become elongated 

 and club-shaped (Fig. 84, n). The antherids bend and 

 come in contact with the oogones, and soon each thrusts 

 out a small tube which penetrates the ofigone, reaching the 



Fig. 82.— Showing 

 conidiophores and 

 conidia of the 

 White Rust of Pe^- 

 pergrass. Magni- 

 fied 400 times. 



