14 



MASS. EXPERIMENT STATION BULLETIN 368 



Single-spore colonies from this culture were obtained by the streak method; 

 i. e., a spore suspension was made in sterile water and streaked on the surface of a 

 petri dish by means of a sterile platinum loop; any isolated colonies which resulted 

 were then transferred to fresh petri dishes. Transfers of these cultures were 

 made and incubated in petri dishes on potato dextrose agar and also in flasks 

 containing elm twigs and sterile water. Twig media of each of the species and 

 varieties of elm used in the experiments were prepared. The inoculations from 

 twig cultures in the following experiments were made from the medium which 

 corresponded to the tree being inoculated. The viability of the organism was 



Figure 9. Trees in Greenhouse with Inoculation Cylinders, on leaf (left), and en trunk (right). 



