Mar. 12 , 19x7 
Fusarium-B light of the Soybean 
433 
erally, but not always, an absence of flesh-colored sclerotia in the soy¬ 
bean fungus. These differences, however, are not believed to be of 
sufficient importance to warrant regarding the soybean strain as a dis¬ 
tinct species ot variety. 
In addition to the media employed in Table II, potato hard agar, corn- 
meal plugs, and string-bean pods were used; but they showed no addi¬ 
tional characters of value. 
Perithecia have never been observed on the diseased stems; neither 
have they been obtained in cultures from the surface spores nor from the 
diseased internal tissues. In fact, the cultural differences between the 
Fusarium sp. on soybean and Neocosmospora spp. are as striking as 
between Neocosmospora spp. and the several species of Fusarium causing 
wilt studied by Higgins (12) and Butler (3). 
INOCULATION EXPERIMENTS 
From the foregoing morphological and cultural studies, it is evident 
that the species of Fusarium on soybean is not distinguished from F. 
tracheiphilum by any well-defined differences. Since the possibility 
existed that they might be separated by biological differences, reciprocal 
inoculation studies were undertaken to secure additional evidence of their 
identity. 1 
Plants were therefore grown in pots and flats in the greenhouse and in 
plots in the field for use in inoculations. The soil used in the pots and 
flats was a fine, compact, sandy loam, except in the case of one experiment, 
and was taken from a field in which diseases of cowpeas and soybeans 
caused by Fusarium spp. had never been observed. In certain of these 
tests, as an added precaution, the soil was partially sterilized by the use 
of a 2 per cent solution of formaldehyde. The seed were also sterilized 
in certain experiments by immersion for 15 minutes in commercial sul¬ 
phuric acid. Since uninoculated plants remained free from disease when 
these precautions were not employed, their use was discontinued in sub¬ 
sequent tests. 
The pots and flats were of sufficient size to permit the plants to grow 
to maturity. 
In determining the percentage of diseased plants, count was made only 
of those in which it was possible to find discoloration and invasion of the 
xylem tissues. In case of doubt in this microscopic examination, planted 
plates were made from the tissues and the subsequent growths studied. 
The varieties of soybeans and cowpeas planted for the cross-inoculation 
experiments were known to be subject in the field to the species of Fu¬ 
sarium on soybean and cowpea, respectively. 
Experiment I—Twenty-five North Carolina Black cowpea and 
25 Mammoth Yellow soybean seedlings, growing in each of two flats 
1 Wollenweber (25, p. 37) says that a consideration of the biological characters is of secondary importance 
in the determination of species. 
