MERCURIC CHLORIDE SOLUTIONS 
347 
silks may germinate and grow down the silks and infest the tip 
of the ear. The most common points of attack, however, are the 
nodes. Here infection takes place after pollen fall. Masses of 
pollen and blown spores of Diplodia zeae are caught within the 
moist leaf sheath where the pollen furnishes a starting medium 
for the fungus which later attacks the base of the leaf sheath and 
nodes. Similar infection takes place within the husk at the base 
of the ear. 
There is no consistent evidence of a migration of the disease 
from the soil up to the ears or higher parts of the plant. Thirty- 
nine per cent of infected ears are borne on unaffected stalks while 
only 22 per cent of all infected stalks showed diplodia higher 
than the third from the ground. Further, but 31 per cent 
of the internodes have been found attacked by the fungus. 
All observations and experiments emphasize the fact that Dip- 
lodia zeae infects locally at any point where blown spores may 
lodge, and that moisture and temperature are essential to growth 
there. 
Department oe Botany, 
Iowa State College. 
EFFECT OF HARDNESS OF WATER ON THE FUN- 
GICIDAL VALUE OF MERCURIC CHLORIDE 
SOLUTIONS 
J. C. GILMAN 
A comparison of the fungicidal value of mercuric chloride 
solutions made up in tap water with those made up in distilled 
water showed that the tap water solutions were much less effective 
in killing the sclerotia of Rhizoctonia solani on potato tubers. Of 
the 182 sclerotia treated with bichloride, 1-1000 in distilled water, 
only 6 or 1.1 per cent grew. In the case of a similar treatment 
of tap water solution of the 139 sclerotia examined, 34 or 7.1 per 
cent grew. Ninety per cent of untreated sclerotia grew in the 
control experiments. 
These facts are important in the application of seed treatments 
where the grower uses hard water in making up disinfecting 
solutions. 
Iowa State College. 
