354 PLANT DISEASES 



small, entire, ovate haustoria. Conidiophores erect, 

 sparingly branched ; conidia generally papillate. Oospores 

 globose, epispore thin, smooth, brownish. 



Plasmopara viticola, Berl. et De Toni, Sacc., Syll., vii. 

 p. 239 (1888) = Peronospora viticola, De Bary. Mycelial 

 hyphae thick, often constricted and varicose, haustoria 

 minute, spherical ; conidiophores fasciculate, coming to 

 the surface through the stomata, slender, 250-850 /x high, 

 branched near the apex ; primary branches 3-5, alternate, 

 secondary branches short, 3-4-furcate, ultimate branchlets 

 pointed, straight, short, usually 4, bearing the ovoid, smooth, 

 colourless, not papillate, very variable in size, smallest 

 8x12 p, the largest 17X30 /* ; oospores subglobose, 

 30-35 /* diam., wall thin, brownish, smooth or slightly 

 wrinkled epispore, often very numerous in dead portions 

 of the host plant. 



Bremia, Regel. Mycelium with vesicular or clavate, 

 simple haustoria ; conidiophores repeatedly dichotomously 

 branched, tips of ultimate branchlets vesicular and bearing 

 several short, subulate sterigmata ; conidia sphaeroid, 

 papillate; oospores globose, minute, epispore yellowish- 

 brown, subrugulose. 



Bremia lactucae, Regel, Bot. Ztg., 1843, P- 665, tab. iii., 

 f. B. Mycelium stout, often contorted ; haustoria clavate, 

 simple; conidiophores 2-6 times dichotomously, or some- 

 times trichotomously branched, ultimate branchlets inflated 

 at the tips, the inflated portion bearing several conical, 

 short spicules, each bearing a subglobose conidium with a 

 broad, depressed apical papilla, 16-23 Pj oospores globose 

 yellowish-brown, pellucid, epispore rugulose, 25-35 /*. 



Peronospora, Corda. Mycelium generally bearing fili- 



