. The fungi which cause plant disease . Plant diseases; Fungi. 96 THE FUNGI WHICH CAUSE PIANT DISEASE radish, and others of minor economic importance. It is cos- mopolitan in distribution. The fungus covers any green part of the host with a dense white growth, often causing hypertrophy especially in oospore forma- tion; conidiophores 200-300 x 10-12 m, bushy branched, stout, deliquescent, with 5-8 main branches, each from 3-7 times branched, ultimate branchlets slender, more or less curved, usually arising at acute angles, about 12-15 x 2-3 m; conidia broadly eUiptic, blimtish, often becommg g
. The fungi which cause plant disease . Plant diseases; Fungi. 96 THE FUNGI WHICH CAUSE PIANT DISEASE radish, and others of minor economic importance. It is cos- mopolitan in distribution. The fungus covers any green part of the host with a dense white growth, often causing hypertrophy especially in oospore forma- tion; conidiophores 200-300 x 10-12 m, bushy branched, stout, deliquescent, with 5-8 main branches, each from 3-7 times branched, ultimate branchlets slender, more or less curved, usually arising at acute angles, about 12-15 x 2-3 m; conidia broadly eUiptic, blimtish, often becommg globose, about 12-22 x 24-27 II, hyaline or very light; oospore globose, yellow-brown, 26-45 ju, epispore smooth or wrinkled; oogonium thick, color- less. P. effusa (Grev.) Rab. causes a serious disease of spinach.*"* It also occurs on a wide range of weeds of the Chenopodiaceae. The species was formerly made to include all the effusae forms of the genus so that literature aboimds with references to it on Viola, Plantago, Polygonum, etc. Hypophyllous, causing yellowish or brown- ish discolorations, the mass of conidiophores of a violet cast; conidiophores 150-400 x 7-9 Mj much branched, the ultimate branches at right angles, usually recurved, 8-15 x 3-4 n; conidia ellipsoid to globose 17-18 x 22-24 n, violet or smoky; oospores globose, 30-40 II, epispore Ught brown, more or less regularly wrinkled; oogonium thin, brown. P. schleideni Ung.*"^ was first described as a Botrytis in 1841. It was noted in America in 1872 by Taylor,'"^ later by Trelease ^"^ and by many others.*"* A very complete description was given by Whetzel *"' in 1904 under the name P. schleideniana. The conidia in mass present a purplish tint. The conidio- phores usually emerge singly through the stomata. The slender, branched haustoria aboimd in the parasitized part often with their ends wrapped around the nuclei. In water the conidia. Fig. 66.—p. effusa on spinach. After Hal- ste
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectfungi, bookyear1913
