276 BOTANICAL GAZETTE [APRIL 
the concentrations of the single salts standing in the same line with 
the datum for the combination, but these proportions are stated at 
the head of the columns of combinations. In those cases where the 
word “‘retardation”’ occurs in the efficiency column, this denotes that 
the efficiency here is much below that of the control without added 
salt, the end point not having been reached at the close of the experi- 
ment in question. 
EFFECT OF SINGLE SALTS 
From the foregoing tables it is apparent that all the salts used 
in this investigation, at some concentrations (both singly and in 
combination), increase the rate of hydrolysis over that of the control 
without added salt; at certain other concentrations they retard 
this process; and at still others they have apparently no influence 
on diastatic activity as measured in this study. Thus, with the 
chlorides of sodium and potassium, used singly, it may be seen that 
with a concentration of m/2048 the effect is practically the same as 
in the control with distilled water. An increase in salt content, 
however (to m/512), results in a slight retardation of diastatic 
action; while with a further increase of added salt (to m/128), the 
point of maximum retardation, as found in this investigation, is 
attained. All higher concentrations used, of these two salts, 
accelerate hydrolysis, the points of maximum acceleration being 
at a concentration of m/8 for sodium chloride and of m/2 for 
the potassium salt. Possibly the most striking feature of the 
results shown in table I is that retardation apparently occurs 
only at relatively low concentrations. To supplement the evidence 
obtained from the experiments, that-there was a retardation with 
. m/128 sodium chloride and potassium chloride as here employed, 
five additional series were carried out with the two salts singly 
at this concentration accompanied by the required controls without 
added salt, all made up and tested in the usual manner. In every 
case a marked retardation was evident in the mixtures containing 
the salts, as compared with the controls. This retardation cannot be 
due to a partial neutralization of the acidity of the diastase by small 
amounts of free alkali present in the salt solutions (the latter were 
very slightly alkaline to phenolphthalein), for table I shows that still 
higher concentrations of these two salt solutions, containing propor- 
tionately more alkali, unquestionably accelerate diastatic activity. 
