Embryo and A leurone Layer of Hordeum . 
1181 
XIII. The Inadmissibility of Copper Sulphate as a 
Sterilizing Agent. 
Copper sulphate, used in the concentration indicated and even in more 
dilute strengths, is unquestionably a most efficient reagent for effecting the 
sterilization of barley seeds, under the conditions described in this paper. 
It was repeatedly demonstrated, by means of several series of steeping 
experiments and subsequent bacteriological examination, that moulds were 
the only organisms which survived after the seeds had been subjected 
to twenty-four hours’ immersion in 10 % copper sulphate solution ; the sur¬ 
vival of these organisms, it is to be noted, occurred solely in a few instances, 
the various types of bacterial flora commonly present on the surfaces 
of cereal seeds being completely annihilated. 
This reagent, however, offers certain disadvantages in an investigation 
like the present one, the chief of them being the difficulty of ensuring the 
complete removal of the last traces of the salt from the seeds by washing in 
water and the consequent risk of thereby introducing a disturbing factor in 
the subsequent culture and digestion experiments, the copper salt, even 
in minute traces, being extremely toxic towards amylase. 
In the initial phases of the work embodied in this paper the culture 
experiments were confined to embryos. In view of the sensitiveness of 
amylase towards copper salts a series of parallel experiments were carried 
out with embryos steeped either in (i) io % copper sulphate or (2) absolute 
alcohol. As the secretory capacities of the embryos in these experiments 
were of the same order of magnitude (such differences as were observed 
being attributable solely to the individualities of the organisms themselves), 
it was concluded that either the salt had been completely removed or its 
amount reduced to such small limits that it could no longer be regarded as 
a disturbing factor. 
When, however, similar experiments were made with isolated aleurone 
layers considerable divergence in their secretory capacities were met with; 
aleurone layers removed from seeds which had been steeped in the copper 
salt solution showed invariably a much lower capacity than aleurone layers 
from seeds which had been steeped successively in absolute alcohol and 
water. This divergence in the results was still more pronounced in endo¬ 
sperms and inner endosperms. In certain experiments with these objects, 
in spite of very thorough washing, the measure of their amyloclastic 
capacities fell from \ to yu of that yielded by similar objects in similarly 
conducted experiments prepared from seeds steeped in absolute alcohol. 
To test the efficiency of attempts to wash out the copper salts, seeds 
were steeped in 10 % copper sulphate for twenty-four hours, then washed 
with sterilized tap water (six re-washings being undertaken), and finally 
4 H 
