78 
IOWA ACADEMY OF SCIENCES. 
5th. The young corn plant shows injury if the seed has 
been immersed for fifteen minutes in water at 60. 5° -61^ C or 
more. 
6th. The young corn plant shows injury if the seed has been 
heated for fifteen minutes in a dry oven at 65"C or more. 
REMARKS. 
The experiments show that corn heated, either dry or in 
water, may be considerably injured and still retain the power 
■of germination; it may show a fair percentage of germination 
and be unable to push through an inch of soil. Hence, mere 
germination does not show the condition of the seed as regards 
vigor. 
Bacteria in the cell cultures are a source of much annoyance. 
If a cell in which the spores do not germinate is found to con- 
tain large numbers of bacteria they may be the cause of the 
failure of the spores to germinate and the experiment must be 
repeated. 
Spores of Fusarium when in immature condition so closely 
resemble the sporidia of corn smut spores that they are easily 
mistaken for them. It is not safe to conclude that the spores 
in a cell are germinating unless the promycelia are actually 
seen coming from the spores. 
PLANT LICE INFESTING GRASS ROOTS. 
HERBERT OSBORN AND P. A. SIRRINE. 
During the fall of 1889 the senior author of this paper deter- 
mined that a species of plant louse, infesting roots of annual 
grasses was identical with the “Dogwood plant louse” {ScM- 
zoneura corni Fabr.), carrying the work far enough to prove 
that the winged forms could be transferred from grass roots to 
dogwood, on which they colonized. As he found the root forms 
principally on annual grasses which were of no economic value, 
it was naturally a question of interest to determine whether 
they might affect forage plants. Furthermore, the occurrence 
of non-migratory forms on certain of the grasses examined, 
