1 1 4 British Fungi. 



latifoUum, Pastlnaca sativa, Petroselinum sativum, 

 Feuceclanum pahistre, Daucus carota, Gonium macu- 

 latum, Meum athamanticum ; also on species belonging 

 to the following genera, Heliosciadium, Laseiyitium, 

 and Selinum. Not uncommon. 



Sometimes sufficiently abundant to form a delicate 

 white bloom on the leaves. The roots of plants in- 

 fested with the Peronospora are often diseased, owing 

 to the presence of permanent mycelium, as in the case 

 of PhytojjJithora infestans. 



Plasmopara densa, Schroet. 



Forming small, scattered, or confluent tufts, white, 

 then yellowish ; mycelium with vesicular haustoria ; 

 gonidiophores 160-180 /u, high, towards the apex 

 divided into 2 — 3 main branches, each with 1 — 3 

 horizontal branches springing from the apical portion, 

 and these again bearing 1 — 3 branchlets ; gonidia 

 broadly elliptical or subglobose, 12-16 or 12-15 x 

 10-12 /Lt, minutely and obtusely apiculate at the 

 apex ; oospores globose, epispore thin, pale yellow. 



Plasmopara densa, Schroet. Kr. Fl. Schles. Pilze, 

 p. 239; Sacc. Syll. vii. 1, n. 814. 



Parasitic on the living leaves of Euphrasia officinalis 

 and Bartsia odontites. Rare. 



Bremia, Kegel. 



Mycelium furnished with vesicular or clavate 

 simple haustoria ; gonidiophores several times dichoto- 

 mously divided, branchlets umbellate, tips inflated in 

 a turbinate or subglobose manner, the swellings give 

 origin to a few (2 — 8) conical, short sterigmata, 



