86 SEMI-CENTENNIAL OF TORREY BOTANICAL CLUB 
tration the more quickly, and for this reason little total growth can 
be attained, although the initial rates are higher than that at 
higher concentrations. The cultures were run in a double series, 
and the concentrations of acid and alkali were varied between 
N/25,600 and N/roo. 
During the course of experimentation it was found that posi- 
tive results in terms of growth could be obtained with alkali when 
` associated with 20 per cent cané sugar, but that acids so associated 
caused the pollen grains or tubes to burst. This again indicated 
the greater swelling effect of acid over alkali. It was then found 
that by increasing the concentration of cane sugar to 40 per cent, 
the effect of acids was held in check and that growth proceeded, 
bursting taking place only at certain concentrations of acid, but 
in the lower of these only after a certain amount of growth had 
been attained. With this difference understood, it was shown 
that the behavior of the growing protoplasm was otherwise and 
in general the same toward both acids and alkalis. Summarily 
stated it is as follows: і 
. At certain concentrations of the reagent, growth proceeds more 
rapidly than in the control, namely, the pure cane-sugar solution. 
The maximum growth occurs for acetic acid at N/3200, for malic 
acid at N/12,800, and for citric acid at N/12,800, or perhaps less. 
Hydrochloric, formic, and oxalic acids did not afford positive 
results in terms of growth, and indeed the evidence for citric acid 
was not unequivocal. This was not because they did not produce 
increased imbibition in the protoplasm, but probably because of 
pathological results which militated against the attainment of 
growth. It is important to note that for those acids which gave 
the data sought, there was less growth for concentrations above 
and below the ones just indicated, and in this we may see a cor- 
respondence with gelatin in its maximum swelling response to 
certain concentrations already mentioned. The correspondence 
is heightened in the growth rates which in low concentrations of 
the reagents are lower than in the control. It was previously 
shown that essentially the same behavior occurs in alkali, sodium 
hydrate having been used. 
That a higher concentration of cane sugar must be used with 
acids may be due to the already acid condition of the protoplast. 
