. Bulletin - Massachusetts Agricultural Experiment Station. Agriculture -- Massachusetts. CEPHALOSPORIUM WILT OF ELMS 19 organism was reisolated from six mc^-e trees on April 8, 1937, gi\ ing a total of twelve successful infections out of fifteen inoculations. Experiitieut 5. Procedure: — Because of the early falling of the leaves in the first attempt to infect elms through the leaves, a second experiment was initiated. February 24, 1937, with a slightly different technique Four young potted seedlings of U. americana L. were placed under a bell jar in the greenhouse; the leaves of two of the t
. Bulletin - Massachusetts Agricultural Experiment Station. Agriculture -- Massachusetts. CEPHALOSPORIUM WILT OF ELMS 19 organism was reisolated from six mc^-e trees on April 8, 1937, gi\ ing a total of twelve successful infections out of fifteen inoculations. Experiitieut 5. Procedure: — Because of the early falling of the leaves in the first attempt to infect elms through the leaves, a second experiment was initiated. February 24, 1937, with a slightly different technique Four young potted seedlings of U. americana L. were placed under a bell jar in the greenhouse; the leaves of two of the trees were injured while the leaves of the other two were left uninjured; a spore suspension was then poured over the surfaces of the leaves of all four trees with care taken that the suspension touched both the upper and under sides. Two similar seedlings were placed under a similar bell jar; the leaves of one of these were injured, sterile water was poured over the leaves of both trees, and they were used as checks. The bell jars were covered with newspaper to protect the trees from the sun. These papers were removed after two days and the bell jars were removed after ten da\ Figure 12. Infected Leaf from Elm Seedlin)>. showing necrotic areas around inoculation wounds. (X 3) Results: — Leaves which had been injured and inoculated soon developed necrotic areas around the wounds, which enlarged to a width of about milli- meters from the edge of the wound; the leaves then gradually became mottled and \ ellow. One leaf turned brown, the edges curled upward, and it finally dropped from the tree, April 12, 1937, less than two months after inoculation (Fig. 12). Another leaf, on the same date, had turned very brown from the tip to about halfway up the midrib toward the petiole; this dry part was decidedly curled and brittle, while the other half of the leaf still showed some green color. The leaf was still clinging to the tree. The leaves which had not been injured show
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