42 
paired single spore cultures of the loose smut produced infection 
on Gothland and the smut was of the loose type, the chlamydo- 
spores being spiny. In the same way, properly paired single spore 
cultures of the covered smut gave ae covered smut type of 
infection on Monarch, the chlamydospores being smooth-walled. 
These results indicate that the infection of ie oats by both smuts 
is dependent upon the proper combination of two definite single 
spore cultures. 
In 1933, many single spore cultures of the loose smut were 
pared with similar cultures of the covered smut and inoculations 
were then made on Gothland and Monarch. Two of these com- 
binations infected Monarch, but the smut resulting was of the 
loose type with spiny-walled chlamydospores. 
i} 
This smut material was saved and used for inoculating a series 
of oat varieties, including Gothland and Monarch, in 1934. Simi- 
lar experiments were carried out in 1935 and 1936 and analyzed 
on the basis of infection and smut types produced, especially on 
Gothland and Monarch. The results may be summarized as 
follows: 
1. Collections or strains of loose smut were obtained capable 
of infecting Gothland, but not Monarch. The pathogenicity and 
other characteristics were typical for the loose smut. Similarly, 
strains of covered smut appeared which were specific in their 
behavior and characteristics on Monarch. 
2. Several strains of the smuts were found which produced in- 
fection on both Monarch and Gothland. ‘The smut produced, re- 
gardless of the oat variety, was typically either loose or covered 
smut. 
3. Gothland was observed to give 15 to 100 per cent. infection 
with certain strains of typical covered smut, to which Monarch 
gave no infection, or at least gave low percentages 
4. Monarch gave 7 to 100 per cent. infection with strains of 
loose smut, to which Gothland usually showed no infection. 
The results indicate that hybridization between the loose and 
covered smuts was accomplished, resulting in the production o 
either loose smut or 
new strains, showing the characteristics o 
covered smut, but differing decidedly in their pathogenic capacities. 
