. Fungous diseases of plants, with chapters on physiology, culture methods and technique . olor 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 ^^- J5/-* ^_ , _-.^. 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 9
. Fungous diseases of plants, with chapters on physiology, culture methods and technique . olor 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 ^^- J5/-* ^_ , _-.^. 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 9ut in darkuniform cirrae. 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 readilv in 36o FUNGOUS DISEASES OF PLANTS. Fig. 178. Septoria Pyricola : Section of Pycnidium nutrient media,germ tubes beingpushed out fromeither end or fromthe middle (). This fungushas been readilycultivated uponbean stems andpear twigs, and Ihave reported thegrowth as follows: Here the fungusgrew slowly at first,producing after sev-eral weeks the pyc-nidia of the several trans-fers this fungus grows quite luxuriantly on bean pods or stems, as seen in fig-ure . . , producing the pycnidia in a short time, and the pycnidia are then notso definite in form but formed of avery loose stromatic mass. The sub-merged hyphae are dark in color, whilethe aerial growth is dense and white,except the stromatic mass inclosingthe pycnidium. I have had culturesfor eighteen months; and althoughthey have been subjected to variousclimatic conditions, nothing of furtherinterest has as yet come from nature the fungus is being c
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