50 



changed. Further inoculation tests would be necessary to estab- 

 lish them as ])ernianent new types. However, the continued and 

 generally constant infection behavior, synii)tonis and morphology 

 of the \?i new smut races add to their ])i-ol)al)le accei)tance as new 

 types and indicate the role hybridization may play in the produc- 

 tion of new races. 



Sorf/Jiiaii Smut InTcstif/nlioiis 



Dr. 1). Elizabeth ]\ Farcy has made further studies on the effect 

 of conditions ol seedling germination on the infection of sorghum 

 with the covered kernel smut. In the spring of 1938 tests were 

 made to determine whether the size of the sand particles in wliicli 

 the seeds were germinated would affect the infection of the seed- 

 lings. Dakota Aml)er Sorgo, a highl)- susceptil)le variety, was 

 used. One set of inoculated seeds was germinated in sand which 

 had |)assed through a 20-mesh sieve but not through a 40-mesh. 

 Another set was germinated in sand which had ])asse(l through a 

 C)0-mesh sieve, "fhe com])arison was made at three different tem- 

 ])eratiu"es, 17.5, 22.5 and 27.5" C. and at hve different degrees of 

 moisture sup])lic>d as water and as a 2 ]X'r cent, sucrose solution. 

 AVhen tlie seedlings were sufhcienth' adxanced they were trans- 

 planted to the field and at maturitv the ])ercentage of infected 

 plants in the various series was determined. 



Seedlings germinated in fme sand at 17.5 and 22.5° C. gave 

 a higher percentage of infected ])lants than those germinated in 

 coarse sand under 12 out ol 14 different combinations of seedling 

 environal conditions. It is probable that the two exce]:)tions were 

 due to some ex])erimental error. When the germination temjxM'a- 

 ture was maintained at 27.5" C, the ]xu"centages of infection were 

 lower when the seedlings were germinated in the line sand as 

 compared with those germinated in coarse sand in all but one case, 

 in which the i)ercentage of infection was i)racticall_\' the same. 



This entire experiment was re])eated with one imjiortant modi- 

 fication. The paraffin ]:)aper cujxs in which the seeds ^\•ere ])lanted 

 were sealed with waxed pa])er and ])araffin, thus ])reventing any 

 exchange of gases between the contents of the cups and the outer 

 air. The percentage of infected ])lants from the sealed cu])s was 

 then compared \^■ith the pei'centage of those from the non-sealed 



