CEREAL INVESTIGATIONS. 
Oct. i, 1925 Sclerotinia Species Causing Decay of Vegetables 617 
of normal dioxygen (3.75): 0.5, 1, 2, and 5 per cent. The microconidia 
were taken from a culture 19 days old. Control hanging drops of 
microconidia in sterile distilled water were run parallel with the aoove 
experiment. Daily microscopic examination was made of all cultures 
for two weeks, but no germination was obtained. The controls as 
well as all other cultures remained inactive. It appears, therefore, 
that lack of oxygen probably is not the cause of poor germination. 
So far as the writer has been able to ascertain, temperature and 
light conditions are not the limiting factors, either in the formation 
or germination of microconidia. To test out the age factor, germina¬ 
tion studies have been carried on from cultures which varied in age 
from 4 days up to 157 days. The microconidia which gave most 
favorable germination were usually from cultures 20 to 30 days old, 
although apparent success was obtained from cultures as young as 
7 and as old as 132 days. Because of the difficulty of definitely de¬ 
termining the time when the microconidia are formed, it is impossible 
to determine at just what age they are most likely to germinate. All 
observations along this line indicate that the microconidia are 
mature as soon as they are formed. No change in color, size, or 
shape is noticeable as the cultures age. 
In all the experiments devised to test the germination of micro¬ 
conidia, approximately 10 per cent were successful. From these 
germinated microconidia, only two cultures ever developed a vigorous 
vegetative growth that could be recovered. These cultures were 
obtained from agar plates, and the greater percentage of other 
successful studies were obtained from artificial or synthetic media. 
In view of this and the fact that no infection of host plants or their 
fresh tissues was obtained, it seems highly probable that the micro¬ 
conidia of the genus Sclerotinia do not play an important r61e in the 
life history of this group of fungi and do not cause infection in the 
field, transit, or storage. 
INFECTION STUDIES 
Artificial infection of a suitable host is readily obtained, under 
favorable conditions, by inoculation with sclerotia, or vigorously 
growing mycelium (pi. 1, D, E, F, and G). The writer’s experiments 
clearly indicate that the limiting factors in obtaining infection are 
moisture and temperature.. More inoculation experiments have 
failed because of lack of water during the first penetration of the host 
tissues than from all other causes. 
Wounds are not necessary for infection, but undoubtedly wounded 
surfaces with their exuding cell contents offering readily available 
food greatly facilitates the progress of the fungus. The succulent 
plants and plant parts are penetrated most rapidly, while the woody 
tissues are much more resistant. This indicates that the mechanical 
make-up of the plant tissues plays a part in resistance to Sclerotinia 
infection. Boyle (7) came to the conclusion that S. libertiana 
effected rupture of the host tissues solely by mechanical pressure. 
He found tnat the mycelium and appressoria of S. libertiana growing 
in turnip juice were surrounded by a mucilaginous sheath which 
fixed and held the “ infection hypbae” to the cuticle of the host. 
He also noticed that the hyphal tips in contact with resistant material 
showed different staining from normal and that the infection hyphae 
