Fungous diseases of plants . may show leaf blight to aconsiderable extent, adjacent plots of budded plants may be seri-ously injured by the leaf spot. The budded stock of the secondyear usually suffers more severely, particularly since it is generallyless cultivated after the first season. In the state of New Yorkmost of the standard varieties may be attacked. Bosc, Anjou,Clairgeau, Seckel, Bartlett, etc., may be considerably injured, butFlemish Beauty, Duchess, and Winter Nellis are more resistant. FUNGI IMPERFECTI 159 The Kieffer is practically exempt. In any case, however, thefungus may be
Fungous diseases of plants . may show leaf blight to aconsiderable extent, adjacent plots of budded plants may be seri-ously injured by the leaf spot. The budded stock of the secondyear usually suffers more severely, particularly since it is generallyless cultivated after the first season. In the state of New Yorkmost of the standard varieties may be attacked. Bosc, Anjou,Clairgeau, Seckel, Bartlett, etc., may be considerably injured, butFlemish Beauty, Duchess, and Winter Nellis are more resistant. FUNGI IMPERFECTI 159 The Kieffer is practically exempt. In any case, however, thefungus may be readily controlled with Bordeaux. The spots on the leaves are few or numerous, angular, and thesize varies greatly with the variety. Three fairly well differentiatedzones of color are shown in an affected spot: at the center it isashen gray, and within this area appear on either surface the minutepycnidia ; the next outer zone, or area, is brown, or black in veryyoung leaves ; and surrounding this second there may be an area. Fig. 177. Dilution Culture of Septoria Pyricola which is purplish in color (Fig. 176). These color details are lostin very old leaves, but the black papillae indicating the pycnidiathen show up clearly. At maturity the spores may ooze out in darkuniform cirras. In cross section the pycnidium is clearly ovate inform. The wall is made up of several layers of dark cells, and thehyaline conidiophores arise from an inconspicuous inner layer(Fig. 178). The spores are flexuous and quite constantly two-septate, measuring about 60 X 3-4 /i. The mycelium is intercel-lular, brownish, and may be detected within the tissues at some littledistance from the perithecium. The spores germinate readily in 36o FUNGOUS DISEASES OF PLANTS
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