Fungous diseases of plants . variable, even upon the same host, undersimilar conditions. f^ 1 ?P^ 1 E^a * ^j2t ^1 ^1 Fk;. 92. Mildew of Cherry 228 f^UNGOUS DISEASES OF PLANTS XXVI. MILDEW OF COMPOSITES AND OTHER PLANTS Erysiphc Cichoracearmn De C. This species of mildew is also widely distributed and occursupon more than two hundred hosts of numerous families. It is unusually common upon spe-cies of Compositas and ingeneral is easily the mostdestructive fungus of thesehosts. It is also well knownto the florist upon speciesof and to the gar-dener upon some varietiesof cucurbits. The fung
Fungous diseases of plants . variable, even upon the same host, undersimilar conditions. f^ 1 ?P^ 1 E^a * ^j2t ^1 ^1 Fk;. 92. Mildew of Cherry 228 f^UNGOUS DISEASES OF PLANTS XXVI. MILDEW OF COMPOSITES AND OTHER PLANTS Erysiphc Cichoracearmn De C. This species of mildew is also widely distributed and occursupon more than two hundred hosts of numerous families. It is unusually common upon spe-cies of Compositas and ingeneral is easily the mostdestructive fungus of thesehosts. It is also well knownto the florist upon speciesof and to the gar-dener upon some varietiesof cucurbits. The fungus is often con-fused with the previous spe-cies. The perithecia areabout equal in size, but theappendages of this formare usually short. The asciare numerous (often 10-15),and Salmon considers thatthe central specific charac-ter lies in the possession oftwo spores. Nevertheless,this species is also variablein every character, and itwill not be easy to distin-guish morphologically between certain forms of the two Fig. 93. Atxr, Persistent Form on Oak. (Photograph by Geo. F. Atkinson) XXVII. MILDEW OF WOODY PLANTS Microsphiera Aliii (Wallr.) Wint. This variable species is typically a fungus of a variety ofwoody plants. It is common upon amentiferous trees and shrubs,but popularly is doubtless best known as the lilac or syringamildew. Upon the lilac the mycelium covers the entire constant is its occurrence upon this host during the late I ASCOMYCETES 229 summer in the United States that one unconsciously associ-ates with the Hlac, during that season, a grayish color. Uponsome hosts, however, the mycelium may form persistent patches (Fig- 93). The perithecium is generally small, with appendages averag-ing i^ times its diameter. These are colorless to light brown inpart, and 3 to 6 times dichotomously branched. The asci areusually 3-8, each containing 4-8 relatively small (18-23 x 10-12 /i) spores. XXVIII. POWDERY MILDEW OF GRAPEUndnida iiccator (Sch
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