16 
BULLETIN 1239, U. S. DEPARTMENT OF AGRICULTURE. 
average temperature of 1.4° C. for 25 days. The first attempts made 
with these cultures failed to yield uniformly satisfactory results, in 
spite of the fact that every precaution necessary to the preparation 
of the medium had been observed. By experiment it was found that 
a perfectly normal spore germination obtained in those cultures 
over which the Petri dish cover had been lifted and pushed slightly 
to one side. Cultures incubated at the same temperature but allowed 
to remain covered germinated indifferently or not at all. It was 
SERES ¥ 
ABC 
Fig. 2.— Location and thickness of strata of bunt-infested soil in an 
experiment to determine the possible relation to Infection of the dis- 
tance between seed and stratum of smutted soil. (Vertical scale, 
each space= one-fourth of an inch.) 
also noted thai in all cases where germination did obtain in the 
covered dishes it was always delayed. It was thus demonstrated 
thai available free oxygen js a factor essential to the normal ger- 
mination of the bunt spore. The same fact has been shown by experi- 
ment with water cultures and with various solid media (Brefeld e1 
al.), but experimental proof of the importance of aeration to the 
wholesale and norma] germination of hunt spores and subsequent 
production of sporidia in or on the soil has not been recorded. 
