Apr. is, 1921 
Susceptibility of Injured Seeds to Molds 
103 
When the attacked seeds germinate, seedling growth is not always 
retarded, such plants occasionally coming up as soon as those of the other 
lots. After the plants reach a height of a few centimeters, however, 
growth practically stops. The plants are weak and often of a paler green 
than the uninjured seedlings, occasionally being somewhat yellowed. 
Actual deformity is not frequent, although the root systems often are 
stunted. When these seedlings are pulled up, the seed is found to be a 
mass of green mycelium. The uninjured seedlings are free from all 
evidences of fungous attack on the seed. 
In a duplicate experiment to determine the relation of injured seed 
coats to susceptibility to invasion by Penicillium, no infection of even 
those seeds injured over the endosperm occurred where the temperature 
remained as low as io° C. throughout. As was found in the blotter 
germinations, Penicillium requires a higher temperature for development. 
In this second experiment the injury to the susceptible seeds was very 
marked in those seedlings grown at the laboratory temperature of 20°, 
and distinct but less conspicuous at the intermediate temperature of the 
window ledge. Further study is needed to determine the optimum 
temperature for development and infection. These experiments indi¬ 
cate that the destruction of seed in the soil by Penicillium is dependent 
on poor physical condition or low vitality of the seed combined with 
temperature and moisture conditions favorable to the development 
of the fungus. 
Besides attacking wheat in the soil, Penicillium is responsible for much 
injury to stored wheat which has not been thoroughly dried. To de¬ 
termine if this injury is also made possible by broken seed coats only, 
some hand-thrashed Early Baart seed was divided into three lots. The 
first was injured by means of a needle scratch over the endosperm, the 
second by a scratch over the embryo, and the third was left uninjured. 
Each lot was divided to make a duplicate set. All were soaked in a 
suspension of Penicillium spores for a few minutes and then put in closed 
, bottles to keep them damp. Penicillium first appeared in the cuts of 
those injured over the endosperm. After two weeks the seed injured 
over the embryo became visibly infected at the point of injury, but at 
the end of three weeks the uninjured seed still showed no signs of fun¬ 
gous attack.' 
The experiment was repeated, using open vials as containers, which 
were kept in a damp chamber. Penicillium spores were dusted on the 
seeds until they were fairly green. In a few weeks green tufts of Penicil¬ 
lium were in evidence on the seed lots with the broken coats, but not 
until nearly two months had passed was there any sign of it on the un¬ 
broken seed. Only 40 per cent of these seeds with unbroken coats germi¬ 
nated at this time, although the original germination was 100 per cent. 
The other seeds were entirely killed (PI. 18, B). 
