no 
Journal of Agricultural Research 
Vol. XXI, No. a 
sulphate solution and suggests that the reason may be the presence of 
invisible imperfections in the testas. He discusses the difference in 
injury determined by germinating treated seed in various soils and in 
filter paper. 
Volkart ( 22 ) gives the results of extensive experiments showing that 
mechanical injury to seed determines treatment injury. He relates the 
thrashing injury to the moisture content of the seed and shows further 
that the location of the break in the testa determines the degree of the 
injury done to the seed by a subsequent dip into copper sulphate. He 
points out that a break over the embryo exposes it to harmful, and in 
many instances fatal, action of the solution. If, however, the seed coat 
is ruptured over the endosperm only, the resultant injury is not serious. 
Burmester (5) said that the injuries received by the seed coat in thrash¬ 
ing made the seed very susceptible to copper-sulphate injury. He found 
that the higher the concentration of the solution used, the greater the 
percentage of injury. Woolman (25) says that most or all of the loss of 
germinative power of treated seed is due to thrashing injury. Wallden 
(23) located the mechanical injury to the seed coats by means of eosin, 
which does not penetrate a sound testa but enters every small fissure, 
staining the seed at that point. He determined that all breaks are rela¬ 
tively unimportant, except those occurring directly over the embryo. 
Seed with uninjured integuments could be exposed to copper-sulphate 
solutions of the highest concentrations without injury. Wallden also 
notes the greater susceptibility of broken grains to molds during storage. 
In confirmation of all these results on the relation of thrashing injury 
of wheat to subsequent injury by copper sulphate, we may report here 
perfect germination of hand-thrashed White Australian, Sonora, Little 
Club, Early Baart, Marquis, Cedar, La Espiga, and Defiance wheat after 
treatment with a 1 to 4 solution (1 pound in 4 gallons) of copper sulphate. 
No sample of harvester-thrashed wheat examined with a hand lens in 
this laboratory has been found to be free from mechanical injury, the 
percentage of seed with the seed coats broken varying from 30 per cent 
to 100 per cent. The extent of the injury varies from an almost impercep¬ 
tible crack to a large tear which leaves the whole end of the embryo ex¬ 
posed (PI. 16). The percentage of germination of such samples after 
treatment varies directly with the percentage of seriously broken seed 
coats (PI. 18, A). Shull (20) States that many seeds have defects invis¬ 
ible even under a microscope, and this may explain why apparently un¬ 
broken seeds occasionally are injured by copper sulphate. 
Table V shows the immunity of the unbroken seed used in our experi¬ 
ments from injury by copper sulphate of any strength with ordinary 
exposures. Hand-thrashed Early Baart seed was exposed to a saturated 
solution of copper sulphate made by dissolving the copper sulphate in 
boiling water until a considerable amount crystallized upon cooling. 
