56 



ered smut, although it has not l)een tested with one or two of each. 

 On the other hanch A. hrcvis has shown high resistance to all the 

 races of the loose smut, although ?^liss Sam])S()n in I'jigland has 

 found a race of this smut which vigorously attacks it. This oat, 

 further, is somewhat susceptihle to several races of covered smut 

 and is extremely susceptihle to at least one. 



Among" the common cultivated oats, two varieties ( P)lack Mcs- 

 dag and Markton) stand out as extremely resistant to all races 

 of hoth smuts. In contrast with these two varieties are Canadian 

 and Victor, Avhich have ]M"oved to he extremely susce])tihle to 

 ]M-actically all the races, hoth Ijeing resistant to one race of loose 

 smut and one of covered smut. These two varieties seem to differ 

 only in the fact that Canadian is suscej^tihle to the Red Rustproof 

 Race of loose smut, wdiile Victor seems to he resistant. Several 

 other varieties, such as Iuu"lv (Gothland and Monarch, show 

 interesting contrasts. Early (iothland is susceptihle to several 

 races of loose smut 1)ut resistant to all races of covered smut, while 

 Monarch is susceptihle to a few races of hoth smuts. So far as 

 determined, however, these two varieties are nex'cr suscejitihle to 

 the same race of either smut. 



The varieties of .Ivcna slcrilis are characterized hy harhoring 

 their own peculiar races of smuts. The Red Rustproof Race 

 seems to he shar])ly limited to this particular group of varieties, 

 while the Fulghum ]\ace is cai);il)le of attacking several varieties 

 of the common oats, as well as the h^ilghtnu strains. 



The diPferent races of smut show certain i)eculiarities. There 

 is one race of loose smut which seems restricted entirely to Avcna 

 harhata although this host, as already noted, seems suscei^tihle to 

 every race of 1x)th loose and covered smut. There is also a race of 

 covered smut which is limited to . /. I'rrris and certain strains of 

 A. strigosa. 



There is soiuc evidence that there is even further dillerentiation 

 among a imml)er of the collections used. .\ few of them seem to 

 he very similar and so have been grouj^ed together as essentially 

 alike, ddierc is, however, some evidence of iiossihle ditferences 

 and further experiments will he necessary to detenuine whether 

 any additional siKialization exists. 



The results ohtained during the ])ast few years have heen i)rc- 

 pared for publication in the IhiHctiii of the Torrey Botanical Club. 



