60 PROTECTION OF PLANTS 1924-25 



Again the most noticeable feature is the very sHght growth made by 16. 

 Culture 23 gave excellent growth and on many of the flasks a mycelial mat that 

 produced spores was formed on the surface of the solution. 



In making a contour that surrounds the cultures giving the largest amounts 

 of mycelium in each triangle, it is noticed that one appears as though it could be 

 fitted into the other almost like a key into a lock. 



The identity of the cultures isolated. 



These have already been compared with those from Leach's work. In 

 comparing them with the results obtained by Barrus and Burkholder, it does 

 not appear that Burkholder's gamma strain has been isolated so far as the pre- 

 sent work goes. Barrus reports pea beans as resistant to the beta strain and 

 Burkholder that the Robust variety is also. In the inoculation experiments 

 White Pea Bean and Robust were resistant to the Canadian cultures used. 

 It was noted that Barrus and Edgerton both reported the Davis, a wax podded 

 bean as susceptible to all strains. Davis' White Wax here seems to be very 

 resistant to all but IV. It cannot, however, be definitely stated that the two 

 varieties are the same. 



An attempt to secure the perfect stage. 



This was a test to see if possibly there were plus and minus strains of the 

 organism. All the cultures were used in this attempt so that the mycelium of 

 every culture would mingle with mycelium from every other. A full test was 

 made on potato dextrose agar and a few selected ones on cornmeal, oat decoction 

 green bean and Czapeck's synthetic agars. but in all cases negative results were 

 obtained. 



Summary and conclusions. 



1. A total of twenty-one cultures was used in a series of inoculation expe- 

 riments on sixteen varieties of beans, results being given from thirteen as the 

 other three were considered consisting of more than one pure line strain. These 

 varieties were selected as a result of a preliminary test with sixty-five varieties 

 inoculated with culture No. I. 



2. Fifteen cultures isolated in the work were used to inoculate the seven 

 varieties that Leach has used as differential hosts and using his dichotomous 

 table they fall within Forms I, II, VIIT. but considering the results as a whole 

 these groupings are not uniform. The n.mount of seed for this experiment was 

 limited and further work is almost certain to modify some of the discrepancies. 



3. Culture 36 (probably from Florida) is considered as a separate strain 

 and identical with IV and by comparing its reactions with those of Barrus' 

 cultures it is considered as belonging to his alpha strain. All of the other cul- 

 tures isolated during the course of the work are considered as coming under his 

 beta strain. Some of the cultures show differences, but it is quite possible that 



