1909-1910-] Parasitic Moulds and Mildews. 203 



In the genus Ovularia, the hyphse or threads are more fully 

 developed than in O'idium, and the one-celled conidia are 

 either solitary or more rarely produced in short chains. The 

 species to be noted are — 



0. veronicce (Fckl.) Sacc, which is frequent on leaves of 

 Germander Speedwell ; 



0. histortce (Fckl.) Sacc, which produces small whitish 

 clusters of conidiophores on the under surface of leaves of 

 Bistort ; and 



0. oUiqua (Cooke) Oud., which is abundant on leaves of 

 Dock, causing withered spots which bear on their lower 

 surface the hyphse and conidia. The latter, however, are 

 very inconspicuous, and often rather hard to detect. 



In the genus Didymaria, the conidiophores are erect, un- 

 branched, and bear at their apex a single ovate - elliptic 

 uniseptate conidium. D. Ungeri Corda is very common on 

 leaves of Creeping Buttercup, where it produces withered 

 spots which bear conidiophores on their lower surface. 



The genus Bamularia is distinguished from Ovularia 

 mainly by the form of the conidia, which are typically 

 two or more septate. This is one of the largest genera of 

 parasitic moulds, and includes a good many species reported 

 as yet only for England, but some of which, however, may 

 probably occur in Scotland. In general, the species occur on 

 leaves of herbaceous plants, and more rarely on those of 

 shrubs and trees. They usually cause discoloured or withered 

 spots, on the lower surface of which the fertile hyphse or 

 threads are produced. The following are some of the most 

 notable species. 



B. idmarice Cooke, — Frequent on leaves of Meadow-sweet, 

 where the conidiophores occur in small whitish clusters on 

 the lower surface. 



R. epilobii (Schn.) — Probably not uncommon on leaves of 

 various species of Willow-herb. 



B. valeriance (Speg.) Sacc. — Locally frequent on leaves of 

 Valerian. 



B. variabilis, Fckl. — On leaves of Foxglove. 



B. calcea (Desm.) Ces. — Frequent on Ground - Ivy, and 

 easily recognisable by the chalk - white clusters of fertile 

 hypha?. 



