. The fungi which cause plant disease . Plant diseases; Fungi. THE FUNGI WHICH CAUSE PLANT DISEASE 181 U. necator (Schw.) ;'' i"*- ^o^ Amphigenous; mycelium subpersistent; perithecia usually epi- phyllous, occasionally hypophyllous or on the inflorescence, more or less scattered, 70-128 ii; cells distinct, rather irregular in shape, 10-20 ii; appendages very variable in number and length, 7-32, rarely up to 40, 1 to 4-times the diameter of the perithecium, septate, thin walled, light or dark amber-brown bas- ally, rarely branched, asci 4-6 rarely up to 9, broadly-ovate or ovate
. The fungi which cause plant disease . Plant diseases; Fungi. THE FUNGI WHICH CAUSE PLANT DISEASE 181 U. necator (Schw.) ;'' i"*- ^o^ Amphigenous; mycelium subpersistent; perithecia usually epi- phyllous, occasionally hypophyllous or on the inflorescence, more or less scattered, 70-128 ii; cells distinct, rather irregular in shape, 10-20 ii; appendages very variable in number and length, 7-32, rarely up to 40, 1 to 4-times the diameter of the perithecium, septate, thin walled, light or dark amber-brown bas- ally, rarely branched, asci 4-6 rarely up to 9, broadly-ovate or ovate-oblong to subglobose, with or with- out a short stalk, 50-60 x 30-40 n; spores 4-7, 18-25 X 10-12 /i. Conidial form (=Oidiumtuckeri), coni- diophores short; conidia elliptic, oblong, or obtusely rounded, 2 to 3-catenulate, hyaline, 25-30 x 15-17 n. Hosts Vitis, Ampelopsis and Actinidia. One of the worst pests of the family. The mycelium is thin walled and spar- ingly septate. The haustoria arise from lobed lateral swellings of the hyphai, penetrate the epidermis with a filamen- tous projection and swell within the host cell to a bladder-like body. The para- sitized cells and later the neighboring pig. iso.—;necator. ii. ones turn brown and die. Perithecium showing/, ap- pendages, and a, asci. IV. The conidia germinate readily in moist Group of asci removed , J. i: .i /• from perithecium emit- air or m water, sending lortn irom one ting «, ascosporea. After to several germ tubes. ^*^' The perithecia are found well developed as early as June or July in the United States and are rather evenly scattered over the affected surfaces. Bioletti ^"^ says that a period of warm moist weather which favors luxuriant mycelial growth, followed by sud- den lowering of temperature to about 50° F., favors their most rapid formation. They are at first hyaline, later brown. After their form and walls become definite, usually during winter, the appendages develop as outgrowths fro
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectfungi, bookyear1913
