. Black rot, leaf spot and canker of pomaceous fruits. Black rot; Leaf spots; Canker (Plant disease); Apples. io8 Bulletin 379 solution of per cent of glucose and 1 per cent of peptone. No cross- wall was developed. After the third day the wall broke and the contents emerged, forming a bud on the surface of the spore. This spherule may attain a diameter of from 35 to 40 /x; its further development was not followed by Delacroix. The writer has observed similar behavior of pycnospores, except that the swollen parts finally developed a germ tube. This took place in tap water. In some cases ol
. Black rot, leaf spot and canker of pomaceous fruits. Black rot; Leaf spots; Canker (Plant disease); Apples. io8 Bulletin 379 solution of per cent of glucose and 1 per cent of peptone. No cross- wall was developed. After the third day the wall broke and the contents emerged, forming a bud on the surface of the spore. This spherule may attain a diameter of from 35 to 40 /x; its further development was not followed by Delacroix. The writer has observed similar behavior of pycnospores, except that the swollen parts finally developed a germ tube. This took place in tap water. In some cases older spores burst and fail to send out a germ tube. The effect of low temperatures on pycnospore germination was noticed in the spring of 1913 in connection with infection experiments. On May 15, 1912, spores in drops of tap water on a glass slide were placed in a petri dish, plenty of water was supplied to prevent drying out, and the culture was placed out of doors, where the temperature ranged between 8° and 10° C. A second culture was kept at room temperature (210 C). No germinations occurred outside, but the cultures kept in the laboratory at 210 C. gave normal germinations. On May 12, 1913, the minimum tem- perature was 90 C, the maximum ° C. All spores out of doors failed to germinate at these temperatures, while those at 210 C. gave normal germination. On May 13,-19, and 20, 1913, when the maximum tempera- ture was i5-5° C, similar results were obtained, except that in one culture on May 20, at ° C, a very low percentage of germination was observed. This indicates that in most cases a temperature of ° C. is unfavorable for germination, and that below that point germination fails. Delacroix (1903 a: 139) states that mature spores germinate after forty-eight hours at a temperature of about 16° C. (°F.). ASCOSPORE GERMINATION (Fig. 30). The ascospores germinate readily in tap water and potato agar. The time required for the process is from six to twel
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectblackro, bookyear1916
