Mar. 12,1917 
Fusarium-Blight of the Soybean 
427 
and animals are also probably concerned in its spread. In all cases 
observed except one, nematodes have been present and probably facili¬ 
tated the entrance of the fungus. The nematodes were found in infected 
sandy soil, but not in infected clay soil. 
COMPARISON OF THE SOYBEAN SPECIES OF FUSARIUM WITH OTHER 
WILT-PRODUCING SPECIES OF THE GENUS 
SOURCE OF CULTURES AND METHODS OF ISOLATION 
Isolations were made from the interior of stems of freshly wilted 
soybean and cowpea plants. The stems were first thoroughly washed 
in water and allowed to remain wrapped in cotton moistened with 
o. 1 per cent solution of mercuric chlorid for 15 ‘minutes. They were then 
split open so that the diseased interior was exposed. Fragments of 
diseased tissue were removed with a sterile scalpel and transferred to 
cooled poured plates of string-bean agar (8 c. c. per plate), to each of 
which four drops of 20 per cent lactic acid had been added. After 
several days, a microscopic examination was made of the conidia and 
mycelium to determine whether other organisms were present. Eight 
transfers to test-tube slants were made from the margin of several 
plantings and kept for comparison and for indications of contamination. 
It may be noted that a large percentage of pure cultures was obtained 
by this method. From the cultures that were pure, single-spore cultures 
were obtained according to the method described by Sherbakoff (20, 
p. 102-103; p. 104, footnote 8). Stock cultures were made from these 
single-spore cultures and repeatedly repoured to protect from subsequent 
contamination. 
Several species of Fusarium were secured, in order to compare them 
with the Fusarium sp. from the soybean and the one from the cowpea, 
isolated as described above. The following species, subcultures from 
Wollenweber's authentic cultures, were obtained through the courtesy 
of Mr. C. W. Carpenter, of the Bureau of Plant Industry: Fusarium 
oxysporum (Schlecht.), F. vasinfectum (Atk.), F. lycopersici Sacc., 
F. niveum Smith (members of the section Elegans), and F. discolor , var. 
sulphureum (Schlecht.) App. and Wollenw. (1, p. 115-118), (section 
Discolor). 
These species were studied in culture, in order to determine their 
morphological and cultural characters, since such a study is considered 
of primary importance in their differentiation. The species mentioned 
were chosen because all except one belong to the section Elegans, the 
section which contains the known wilt-producing species, and because, 
according to Wollenweber, they are the most difficult to separate by this 
method. F. conglutinans Wollenw., F. redolens Wollenw., and F. ortho - 
ceras App. and Wollenw., of the same section, are included in the com¬ 
parisons. They are so different from the others, as indicated by the 
