. The fungi which cause plant disease . Plant diseases; Fungi. 184 THE FUNGI WHICH CAUSE PLANT DISEASE Fig. 133.—p. oxycan- t h a e, appendage tips. After Sal- mon. Spirea and Vaccinium. Especially damaging to cherry and apple. Throughout the northern hemisphere. P. tridactyla (Wal.) De Bary is considered by Salmon ^'^ as a variety of the last species. Hosts: Plum and other species of Pnmus and of Spirea. Similar to the preceding in habit and general character but differing in more critical charac- ters. Perithecia 70-105 fi; cells 10-15 /i; ap- pendages 2-8 usually 4, 1 to 8-times the diamete
. The fungi which cause plant disease . Plant diseases; Fungi. 184 THE FUNGI WHICH CAUSE PLANT DISEASE Fig. 133.—p. oxycan- t h a e, appendage tips. After Sal- mon. Spirea and Vaccinium. Especially damaging to cherry and apple. Throughout the northern hemisphere. P. tridactyla (Wal.) De Bary is considered by Salmon ^'^ as a variety of the last species. Hosts: Plum and other species of Pnmus and of Spirea. Similar to the preceding in habit and general character but differing in more critical charac- ters. Perithecia 70-105 fi; cells 10-15 /i; ap- pendages 2-8 usually 4, 1 to 8-times the diameter of the perithecium, apical in origin, more or less erect, apically 3-5 or 6-times dichotomously branched, primary branches usually more or less elongate, sometimes slightly recurved; asci globose or subglobose, 60-78 X 60-70 n; spores 8, 20-30 x 13-15 /*• Chiefly European but found also in Asia and America. P. leucotricha (E. & E.) Salm. Mycelium amphigenous, persistent, thin, effused; perithecia densely gregarious, rarely more or less scattered, 75-96 /t, sub- globose, cells 10-16 n; appendages of two kinds, one set apical the other basal; apical appendages 3-11 in number, more or less widely spreading, or erect-fasciculate, 4 to 7-times the diameter of the perithecium, apex undivided and blunt or rarely once or twice dichotomously branched, brown basally; basal appendages nearly obsolete or well developed, short, tor- tuous, pale brown, simple or irregularly branched; ascus oblong to subglobose, 55-70 x 44-50 ft, spores 22-26 x 12-14 fi, crowded in the ascus. Conidia (=Oidium farinosum): ellipsoid, trun- cate, hyaUne, 28-30 x 12 fi. Primarily American but occurring in Europe and Japan. A most serious pest of the apple. This and P. oxyacanthae, the apple mildews of America, have been variously treated by writers ^°- P*"7^- ^™ ,-, , t m, cotncna, so that the literature presents an almost inex- tricable tangle as has been pointed out by Pam- mel and by Stewart,
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectfungi, bookyear1913
