8 MASS. EXPERIMENT STATION BULLETIN 368 



removed from the culture by means of forceps and washed in a drop of distilled 

 water on a glass slide. The resulting spore suspension was then examined under 

 the microscope. The spores are hyaline and vary in shape from ovoid to fusiform 

 to allantoid (Fig. 5). They contain oil globules; the size varies from 2 to 6 microns 

 by 6 to 20 microns with probably a small percentage either larger or smaller. The 

 average size of spores computed from five different cultures is 4.6 by 1L4 microns. 



Figure 5. Conidia of the Causal Fungus of the Elm Wilt, (x 1000) 



The mycelium is finely branching, hyaline, and septate; it anastomoses fre- 

 quently. The branching is irregular (Fig. 7), with an angle of approximately 

 90" at the fork. The hyphae may be 6 microns in diameter but the terminal 

 hyphae are smaller and more threadlike in appearance. Large spore masses 

 similar to those described by Buchanan were found in many cultures, especially 

 where the aerial mycelium was not abundant. 



The ease with which the organism may be cultured is illustrated by an incident 

 which occurred during the routine work in the laboratory. After tissue plantings 

 had been made, the elm specimens, in envelopes, were placed in a wooden file 

 until the cultures should be ready for examination. When the specimens were 

 removed for comparison with their respective agar plates, it was found that one 

 drawer was swollen and the specimen envelopes were decidedly moist. In three 

 of these envelopes were twigs the tissue plantings of which showed growth of 

 Cephalosporium sp. These twigs were covered with tufts of mycelium growing 

 out through the lenticcls. Cultures were made from the h>'i)hae taken from each 

 specimen. These cultures all \ icidcd growth of Cephdlnsporiuui sp. and one twig 

 yielded a pure culture. 



