. Bulletin of the Department of Agriculture. Agriculture; Agriculture. APPLE BLOTCH AND ITS CONTROL. [x. When newly formed it is easy to demonstrate the presence of a gelatinous covering about the spore, especially when, as is often the case, it is prolonged into a stout hyaline appendage (fig. 2). The spores (fig. 3) germinate in 15 to 20 hours. The germ tube is some- what darker than the spore and usually shows a pronounced thickening at the point of emer- gence (fig. 3). More than one germ tube may issue from a single spore (fig. 3). Spores from the twig cankers in which the fungus
. Bulletin of the Department of Agriculture. Agriculture; Agriculture. APPLE BLOTCH AND ITS CONTROL. [x. When newly formed it is easy to demonstrate the presence of a gelatinous covering about the spore, especially when, as is often the case, it is prolonged into a stout hyaline appendage (fig. 2). The spores (fig. 3) germinate in 15 to 20 hours. The germ tube is some- what darker than the spore and usually shows a pronounced thickening at the point of emer- gence (fig. 3). More than one germ tube may issue from a single spore (fig. 3). Spores from the twig cankers in which the fungus has passed the winter are usually mature and ready to infect the young fruit and leaves about three weeks after the petals have fallen. This was first determined by Scott and Rorer by noting the latest time at which spraying would effectively 'prevent infection. The time of infection was directly determined by the writer during the seasons of 1914 and 1915 by germination tests of spores from twig cankers. Table I shows the results of such Fig. 3.—Germinating spores of Phyllo- Sticta solitaria. Spores from Ben Davis twig cankers. May 25, 1914. Table I.—Results of germination tests of spores of apple blotch from twig cankers. Date. Germi- nating sjpores. Date. Germi- nating spores. Date. Germi- nating spores. 1914. Per cent. 0 0 0 0 2 1914. Per cent. 0 0 75 75 75 1915. May 13 Per cent. 10 May May 17 20 May 6 May 23 May 21 20 May 8 May 24 75 May 9 May 29 May28 75 For each test, pyenidia were scraped from the newer portions (the current year's growth) of young twig cankers. These pyenidia were then examined under the microscope for spores. If spores were suffi- ciently abundant and appeared to be mature, they were suspended in distilled water in Van Tieghem cells and the percentage of germinat- ing spores was noted daily for periods ranging from three to five days. As the spores when mature usually germinate within 24 hours, it was really unnecessary to pr
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