48 



ard White Milo and [baekhull Kafir were also grown. The num- 

 ber of infected plants was considerably lower than was obtained 

 the previous year; a total of I2<] plants were inoculated and 8 ( (\2 

 per cent.) were infected. 



The results suggest that in the crosses involving Feterita and 

 Sumac Sorgo and Feterita and Dawn Kafir, susceptibility is 

 dominant in the second generation. ( hi the other hand, in the 

 cross between Standard White Milo and Hlackhull Kafir resistance 

 is dominant. So far, we have not been able to completely over- 

 come the difficulty encountered in securing the infection of the 

 maximum number of susceptible plants -of the parent as well as 

 of the hybrids. As noted from the data presented, the susceptible 

 parent frequently falls far below the maximum amount of in- 

 fection, and has proved quite vaiiable in the different experiments 

 in succeeding years. It would be much easier to interpret the 

 results if methods could be devised for use on a large scale for 

 securing the infection of all the susceptible individuals. However, 

 it appears quite clear from our experiments extending over a 



while in others this quality is recessive. 



Head Smut of Corn and Sorghum 

 Our earlier experiments on the head smut of corn and sorghum 

 (Soros pot-in tn Rcilumitm) dealt with the problem of possible 

 l'io i« to i, q> ■ lali/ation in the smuts collected on each of these 

 groups of host plants. Extensive experiments were carried out, 

 and clear-cut evidence obtained that die smut on sorghum is higbh 

 •"• i ill ! to that ■ rop whili die smut on corn is equally special- 

 ized to corn. Our results bearing on Ibis problem have been pub- 

 lished during the past year. 



Some additional lines of investigation have been followed up. 

 One of the main ones has to do with the duration of the sus- 

 ceptible period of seedlings, and also tire bearing o[ the age of the 

 spore-soil mixture on its capacity for infecting. A large num- 

 ber of combinations were made during the past year. bYequenllv 

 too per cent, infection of the plants was secured. 1 ligh infections 

 were obtained usin t hb p epared oi oil mixture and dry 



