83 



tional races have been isolated by the use of other oat varieties to 

 differentiate collections which had been previously grouped together. 



The 15 races of covered smut now established showed high in- 

 fections on Gothland, while Monarch was resistant to 11 and 

 susceptible to 4 of these races. Early Champion was susceptible 

 to all of them, while Fulghum and Joanette were resistant to all. 



Eight of the 9 loose smut races which have been differentiated 

 gave high infections on Monarch ; Got bland was susceptible to 6 

 of these races and resistant to the remaining 3. Green Mountain 

 and Early Champion, susceptible to race 1 of the loose smut, were 

 resistant to all the races, while Fulghum and Joanette, resistant to 

 race 1 of the loose smut, were- fully susceptible. 



Two collections of the covered smut and 4 of the loose smut 

 reacted on various oat varieties in the same manner as the original 

 races of these smuts which were crossed. 



In the experiments carried out, quite high percentages of in- 

 fection were usually obtained. 



Sorghum Sin it I Investigations 



Sorghum smut investigations were continued by Dr. D. Eliza- 

 beth Marcy. 



Effect of Endosperm Removal upon Infection. — Earlier reports 

 have indicated that certain conditions which retard seedling growth 

 also increase infection with the covered smut of sorghum. Seed- 

 lings germinated in sand moistened with sucrose solution usually 

 give higher infections than those germinated when water is used. 

 Another method of stunting seedlings is the removal of part of 

 the seed endosperm before inoculating and planting. This method 

 involves rather serious loss of seedlings in the susceptible Dakota 

 Amber Sorgo. However, all of the surviving plants were smutted, 

 while 94 to 97 per cent, without endosperm removal were infected. 

 With Red Amber Sorgo, 49 per cent. o1 the endosperm deficient 

 seedlings were smutted, as against 31 per cent, of the controls. 

 The effect of endosperm removal on the peculiar type of infection 

 displayed by Feterita termed " blasting " was also tested. Again, 

 many of the endosperm deficients failed to survive, but 29 per cent. 

 of the survivors were blasted, as against 18 per cent, of the controls. 



