122 DISEASES OF CULTIVATED PLANTS 



of mildew on the under surface of the leaves of species of 

 Aster and Erigeron. 



Conidiophores cylindrical, whitish then tinged brown, apex 

 slightly inflated, bearing a few slender sterigmata, each carry- 

 ing an elliptical, papillate conidium, 20-25X12-14 /*. 

 Oospore globose, wall thick. 



Plasmopara pygmaea (Schroter). Forms minute tufts of 

 mildew, white at first then greyish, on the under surface of 

 leaves of Aconitum, Anemone, Jfepatiea, Zsopyrum, and other 

 ranunculaceous plants. 



Conidiophores slender, simple or sparingly branched, tips 

 with a few slender branchlets (sterigmata), each bearing an 

 elliptical conidium, having the apex broadly and obtusely 

 papillate, 1S-25 x 15-2011. Oospore globose, wall brownish, 

 smooth or minutely rugulose, 44-45 n diam. 



Plasmopara nivea (Schrot.). Grows on the under surface of 

 the leaves of various umbelliferous plants, as Aegopodium, 

 Anthriscus, Angelica, Pimpinella, Stum, Daucus, etc., etc. 



Conidiophores simple or slightly branched, conidia broadly 

 elliptical, apical papilla indistinct, 21-25X15-18 /x. 

 Oospore irregularly globose, brownish, smooth or slightly 

 rugulose. 



The conidiophores sometimes are crowded and form a 

 delicate white mildew on the leaves. The mycelium is known 

 to be permanent in the root of some of the host-plants. 



Plasmopara densa (Schrot. ). is parasitic on the under surface 

 of the leaves of Bartsia odontites and Euphrasia officinalis % 

 where it forms small scattered white, then yellowish patches 

 of mildew. 



Conidiophores slightly branched, conidia broadly elliptical 

 or subglobose, minutely and obtusely apiculate, 12-16x10 

 12 \i. Oospore globose, pair yellow. 



SCLEROSPORA (SCHROT.) 



Conidiophores erect, simple or sparingly branched, conidia 

 ovate, zoospores escaping through the ruptured apical papilla. 

 Oospores globose, epispore brown, very thick, multistratose. 



Sclerospora macrospora (Sacc.) has been recorded as occur- 

 ring on the male flower of maize. Springing from the stomata 

 dendritic tufts of mycelium were observed, which were con- 

 sidered to represent a hitherto unknown conidial condition 

 of the fungus. 



