Apr. 15, 1921 
Susceptibility of Injured Seeds to Molds 
119 
The data in Table XII indicate that wheat will withstand the pene¬ 
tration of a saturated copper-sulphate solution for a longer time at the 
low temperature of the refrigerator than at the higher ones of the 
laboratories and incubators. If the increased permeability occurs as the 
result of chemical changes, we might expect a very exact relationship 
between temperature and the resistance of the seed to the penetration 
of copper sulphate. The preceding experiment and others indicate some 
such correlation. 
SUMMARY 
(1) An unbroken seed coat ordinarily affords absolute protection 
against attack of living seeds by Penicillium or Rhizopus in damp 
storage, in the soil, or in blotter germinations. Infection of such seeds 
has been obtained, however, by retarding germination of the seed by 
means of low temperatures. 
(2) The location of a break in the seed coat determines the ability of 
saprophytic fungi to invade seeds, either in the soil, in storage, or in 
blotter germinations. If the injury is over the endosperm, 100 per 
cent fatal infection results when the spores of Penicillium or Rhizopus 
are present; but if it is over the embryo, the seeds remain practically 
immune. 
(3) The vitality of seeds is a factor in determining the ability of Peni¬ 
cillium and Rhizopus to attack them. Death or injury resulting from 
seed treatment, or other cause, renders previously immune seeds imme¬ 
diately susceptible. Even perfect seed coats no longer are a protection. 
(4) No visible infection with either Penicillium or Rhizopus occurred 
where the temperature remained as low as io°C. throughout the experi¬ 
ment. 
(5) Penicillium requires an atmospheric humidity of at least 80 per 
cent for its development on stored wheat. Aspergillus will grow on 
wheat at a humidity of 70 per cent. 
(6) These molds develop more slowly on stored wheat and barley 
which has been treated with copper sulphate or formaldehyde than on 
equally moist untreated wheat. Penicillium is especially sensitive to 
formaldehyde. 
(7) Although a break in the testa over the endosperm of wheat does 
not result in any injury to the germ upon short exposures to copper 
sulphate, injury becomes apparent after exposures of an hour, showing 
that the poison eventually is absorbed through the endosperm and 
scutellum. A similar break over the embryo results in its death after 
exposures of only three to five minutes. 
(8) When seed coats are badly injured, liming does not prevent ex¬ 
treme injury, because the copper sulphate enters such seeds quickly. 
When the seeds are only slightly injured, a lime dip is effective in neutral¬ 
izing the solution before injury occurs. 
