. Annual report of the Agricultural Experiment Station. Cornell University. Agricultural Experiment Station; Agriculture -- New York (State). 190 Bulletin 236. 4, The Cause of the Canker. Fig. 62.—Typical New York apple tree can- ker, caused by the fungus Sphacropsis malo- ri(m. Comparatively young canker. Observe the little pimples covering the diseased bark, —the sporecases of the fungus- A microscopic examina- tion of the viscid milky drops that exude from freshly cankered surfaces (Fig. 51) on moist cloudy days shows them to be com- posed almost entirely of minute rod-shaped bacteria. The
. Annual report of the Agricultural Experiment Station. Cornell University. Agricultural Experiment Station; Agriculture -- New York (State). 190 Bulletin 236. 4, The Cause of the Canker. Fig. 62.—Typical New York apple tree can- ker, caused by the fungus Sphacropsis malo- ri(m. Comparatively young canker. Observe the little pimples covering the diseased bark, —the sporecases of the fungus- A microscopic examina- tion of the viscid milky drops that exude from freshly cankered surfaces (Fig. 51) on moist cloudy days shows them to be com- posed almost entirely of minute rod-shaped bacteria. The diseasetl tissue within the bark is also found to be alive with these minute plants. By their rapid growth and multiplication within the cells of the bark, they cause its death. They are not carried along in the sap but slowly work their way from cell to cell. When the canker dries down they die and disappear, so that examination of the tissue of old cankers does not show them. That they are the direct cause of the dis- ease was proved in the fol- lowing way: Bacteria from the cankered tissue were in- troduced into the bark on the body of a healthy apple tree and also into the bark of a healthy pear tree, with the result that typical cankers appeared in both cases. (Figs. 65 and 66.) Blossoms and growing twigs of both pear and apples were also inoculated with bacteria from this same canker. These nearly all developed good cases of blight (Figs. 67, 68 and 69) in about ten days,. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Cornell University. Agricultural Experiment Station. Ithaca, N. Y. : The University
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