1916] 
GILMAN—CABBAGE YELLOWS 39 
the sterile flats was inoculated by stirring into its surface ten 
pure cultures of F. conglutinans which were sporulating 
abundantly. Then all the flats were planted. As an addi- 
tional control, a flat of normal greenhouse soil was placed 
in the series. On July 7 yellows began to appear in the steril- 
ized inoculated flat and continued to spread until July 16, when 
the experiment was concluded by making plates from the 
plants from the sterilized inoculated, and the sterilized flats. 
F. conglutinans was found as the cause of the yellowing in 
all the plants, while the control plants remained sterile. This 
is shown well in pl. 2, figs. 15 and 16. Exact counts were not 
made. 
Again, on June 29, four pots of sterile greenhouse soil were 
inoculated with cultures of F. conglutinans, and on July 24 
yellows was found in all four of the pots. On July 11 inocu- 
lations of individual plants were repeated by dipping 
wounded plant roots into suspensions of the spores of the fun- 
gus in sterile water. Adequate controls were included in this 
series and in all cases the control plants remained healthy, 
while among the inoculated plants, 50 per cent of the indi- 
viduals showed the characteristic symptoms on July 24, when 
the experiment was discontinued. 
VIRULENCE OF CULTURES 
Pure cultures of F. conglutinans vary greatly in their viru- 
lence, and the cause of this variation is not certain. From 
inoculation experiments it would seem that, in general, the 
longer the organism has been carried in culture the greater 
is the probability that it has lost its virulence. On the other 
hand, drying in culture seems to have little or no ill effect 
on the virulence of the organism. 
The susceptibility of the host must also be considered as 
an important factor when the fungus-host relation hangs in 
such a delicate balance, and the source of the culture is always 
