Embryo and Aleurone Layer of Hordeum . 11 77 
The barley used in these experiments and those which follow was 
finely ground in a Seek mill and afterwards passed three times through 
a finely-meshed horsehair sieve in order to secure uniformity of sample. 
The bulk sample prepared as described was conserved during the progress 
of these and the experiments which follow in a desiccator over H 2 S 0 4 and 
carefully shielded from the light. 
The values given in the above and following tables have been 
corrected by deducting the copper-reducing values of similarly conducted 
control digestions with boiled preparations of secretions and barley sub¬ 
stance. 
Experiments i and 2 give the separate amyloclastic powers of the 
embryo secretion and barley substance respectively. Experiment 3 shows 
clearly that the combined activities of the embryo secretion and barley 
substance roughly correspond to the sum of their separate values ; each 
enzyme apparently retains its individuality and behaves as an independent 
unit. There is no evidence in this experiment of either activation or 
inactivation. 
Where, as in Experiments 4 and 5, the influence of boiled barley sub¬ 
stance or boiled embryo secretion on the embryo secretion and barley 
substance respectively is investigated, there is positive evidence of in¬ 
activation. The amyloclastic power of the embryo falls from 208 mg. to 
I 59 while that of the barley substance decreases from 343 mg. to 
310 mg., and the results so far considered negative distinctly the sugges¬ 
tion that activation of the amylase of the resting grain is produced by the 
amyloclastic secretion of the embryo. 
Consideration of Experiments 3, 4, and 5 once more raises the question 
of what constitutes a control. If, for example, the sum of the values 
of Experiments 4 and 5, regarded for present purposes as of the nature 
of control experiments, viz. 159 + 310 = 469 mg., be compared with the 
value furnished by Experiment 3, which equals 556 mg., then it would 
appear, in the absence of the results of Experiments 1 and 2, as though the 
amylase of secretion and barley amylase had mutually activated each other. 
Similar examples will be met with in the other series of experiments 
described in this section ; these will serve to emphasize the fact that experi¬ 
ments devised to show whether inactivation or activation of a given enzyme 
does or does not occur require special circumspection in the matter of 
design. 
Below are given the results of similarly conducted experiments with 
the aleurone-layer secretion and barley amylase. 
