Classification . 107 



Analysis of the Genera. 



A. Gonidia catenulate, formed within the tissues of 



the host. 



Cystopus. Gonidia and oospores producing zoo- 

 spores. 



B. Gonidia solitary^ borne on gonidiophores that 

 emerge from the matrix into the air. 



Fliytoplitliora. Gonidia producing zoogonidia, at 

 first produced terminally on the gonidiophores, then 

 apparently laterally also. 



Plasmopara. Gonidiophores sparingly branched. 

 Oospore with a thin, smooth wall. 



§ Gonidiophores repeatedly dichotomously branched, 

 terminal branchlets subulate, curved. 



Bremia. Haustoria of mycelium branched ; gonidia 

 papillate at the apex, germ-tube emerging from the 

 papilla. 



Peronospora. Haustoria of mycelium not bi^anched ; 

 gonidia not papillate, germ-tube issuing laterally, 



Cystopus, Lev. 



Gonidiophorous hyphse short, simple, smooth, 

 cylindrical or clavate, very obtuse, springing in 

 fascicles from the mycelium, bearing a single row of 

 concatenate gonidia at the ajoex ; gonidia either all 

 alike, colourless, giving origin to zoospores, or the 

 terminal gonidium is furnished with a thicker, 

 yellowish membrane, and germinates by the emission 

 of a tube, or is sterile. The sori remain covered with 

 the epidermis until the gonidia are mature, and 

 then burst through. Oospores globose, epispore 

 usually reticulated or warted. 



