40 



as numerous collections of smuts in order to determine the 

 possible limitations of the different strains. 



The Influence of Environal Factors on Oat Smuts. — Previously, 

 studies have been carried out to determine the influence of 

 temperature, moisture, etc. on the infection of oats by the covered 

 smut {Ustilago levis). During the past year similar experiments 

 have been carried out to determine the influence of certain 

 environal factors on infection by the loose smut {Ustilago avcnae). 

 At the same time, the covered smut was also grown for com- 

 parison. The temperature and moisture ranges for the loose 

 smut are very similar to those for the covered smut. Infection 

 occurs over a wide range of soil temperatures. The maxinmm 

 appears to be around 20° C. 



Inheritance of Smut Resistance. — Additional progress has been 

 made in the study of smut resistance in certain oat crosses. Very 

 defmite results as to the resistance of certain segregates have been 

 secured. The field experiments in general have coincided some- 

 what closely with the cultures grown in the greenhouse. How- 

 ever, as a rule, lower infections were obtained and the data are 

 not so-easily analyzed. 



Investigations with Sorghum Smuts. By George M. ReI':d and 



James A. Vx-ris 



New Method of Infection in Loose Kernel Smut of Sorghum. — ■ 

 The most important result obtained with sorghum smuts has 

 been the demonstration of a new mode of infection in the loose 

 kernel smut (Sphacelotheca cruenfa). Heretofore it has been 

 assumed that infection takes place through the young seedling 

 of sorghum by means of spores carried on the seed, or, rarely, 

 in the soil. That such seedling infection does occur has been 

 clearly demonstrated. If the infection occurs in the seedling 

 stage, the host plant is noticeably dwarfed, tillers out extensively, 

 and heads out early. The spores produced in these heads are 

 more or less widely distributed. Some of them may be carried 

 to the young developing heads on lateral branches of normal 

 plants and there give rise to an infection which in a short time 

 may result in the appearance of smutted heads on plants whose 

 terminal head is normal. In some cases, all the flowers In the 



