[ VoL. 3 
42 ANNALS OF THE MISSOURI BOTANICAL GARDEN 
The cultures were all prepared in the same way for the 
experiment. They were all grown on cooked potato stems, 
and were of the same age. Each culture was used to inoculate 
five plants by inserting a bit of the mycelium into the hypo- 
cotyl of young seedlings still in the cotyledonous stage. 
The previous history of the cultures, of course, differed 
for the individual. Cultures VI, XVII, and XIX had been 
allowed to dry out on potato hard agar for fourteen months, 
that is, from July 14, 1913, to September 26, 1914, and then 
were transferred to cooked potato stems. On January 12, 
1915, they were again transferred to fresh cooked potato 
stems, and these cultures were used in the experiment. Al- 
though two of them (VI and XVII) apparently lost their 
virulenee, the third (XIX) retained its ability to attack the 
host even after this severe drying. Other strains which had 
not been allowed to dry out but which were kept on fresh 
media, possessed no greater virulence, nor did any greater 
percentage of them exhibit pathogenicity. 
The length of time the organism has been in culture seems 
to be a more important factor; for cultures isolated late in 
1914 showed proportionally a larger number virulent than did 
those isolated at earlier dates. In addition, the more recent 
isolations showed the greater virulence. That this is not 
invariable, however, is shown by the fact that many of the 
cultures first isolated still retained their virulence, viz., ХХХ, 
XXXII, XXXVII, all three of which were isolated on June 
28, 1912. 
The source of the culture seems to have greater influence. 
Of the six strains of F. conglutinans isolated from cauliflower 
grown in diseased soil and apparently attacked with yellows, 
but one (XX) showed any ability to infect cabbage and that 
only to a limited extent. Strains from aster and potato, 
kindly furnished by Dr. W. J. Morse of the Maine Agricultural 
Experiment Station, also gave negative results when inocu- 
lated into cabbage. F. orthoceras, which had been isolated 
from the stem of a diseased cabbage plant, was introduced 
into the series as a control. A number of undetermined Fu- 
sarium cultures which had been isolated from cabbage, cauli- 
