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\s. 



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 1.5 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 showed no evidence of the entry of the 

 fungus, but presented the same appearance as the two checks. 



On July 9, 1937, all the seedlings were removed from the soil, the leaves re- 

 moved, and the stems and roots cultured in the following manner: the seedling 

 was immersed in 75 percent alcohol and allowed to dry under aseptic conditions; 

 the stem was then cut into short sections which were placed in a petri dish of 

 potato dextrose agar, and the root was similarly cut and placed in another dish. 

 After incubation it was found that Cephalosporium sp. had grcwn from the sec- 



