52 PROTECTION OF PLANTS — 1925-24 



of infection evident upon the seedling. Five classes were made taking in as far 

 as possible an equal range of infection. Fig. 1 illustrates this. 



VR stands for "very resistant" and the plants only show a reddish flecking. 



R stands for "resistant" and the plants show small lesions that do not deve- 

 lop into typical anthracnose spots. 



SR stands for "slightly resistant". The plants show many small lesions 

 that do not develop but with them are lesions that interfere to a slight degree 

 with the growth of the plant. This division includes the doubtful cases of resis- 

 tance and susceptibility and according to observations a difference in envi- 

 ronmental factors might easily place these into either the resistant or susceptible 

 groups. 



S stands for "susceptible". The plants produce typical lesions that deve- 

 lop acervuli and spores by the time the records are taken. 



CS stands for "completely susceptible". The plant is dead or so nearly so 

 that it will not recover. 



The taking of records was often rendered difficult by reason of the different 

 effects on bean varieties as for example on pea and wax beans. 



Discussion of Tables. 



The following table shows the reactions of all the cultures isolated during 

 the w^ork on thirteen varieties of beans. Three other varieties, Well's Kidney 

 Wax, Selected Canadian Wonder, and Dwarf French Excelsior, were also used 

 in this experiment, but a few beans were found in each that gave such a different 

 type of infection that they were left out. These varieties were therefore not 

 considered as being pure line strains and possibly they did not constitute a pure 

 variety. 



A study of Table II shows five varieties that gave a uniform reaction to all 

 the cultures; Well's Red Kidney is one of these; the difference noted being 

 attributed to a change in weather conditions as one part was inoculated on a 

 fine day and the rest on a rainy. In considering the remaining eight varieties, 

 it is noticed that the majority of the cultures give nearly identical results on 

 the bean varieties. Cultures, 2, 4, 5, 26 and 31 are identical in their infection 

 capacities, 6, 25 and 29 vary but little from them, and 1, 30 and 32 vary a little 

 more widely but only on the White Pea Bean which was the first to be inocu- 

 lated. It is quite possible that errors might have crept in that would explain 

 any such minor differences, especially so in this case for it has already been 

 pointed out that with pea beans it is often difficult to be certain of the degree 

 of infection. Culture 33 varies more widely still and is resisted by a variety 

 that was completely susceptible to all the other cultures and is infectious on a 

 variety that constantly shows varying degrees of resistance to other strains. 



The remaining four cultures vary quite markedly. Yellow Six Weeks is 

 completely susceptible to culture 36 and this is a variety that is very resistant 

 to all of the other cultures. Culture 36 also shows a slight difference on large 

 White, 0-713 and on this variety gives a similar reaction to 16 and 35. Cul- 



