Feb. 2 ,1924 
Tissue Fluids in Cotton 
Two possible explanations of the decrease in osmotic concentration, 
specific electrical conductivity, and hydrogen-ion concentration from 
the first to the second series will at once suggest themselves. 
Soil moisture may have been greater or, due to the retardation of 
growth toward the end of the season, the requirements for soil moisture 
may have been less, in the second than in the first series. As a con¬ 
sequence of either of these conditions, the turgidity of the leaves may 
have been somewhat higher in the second series. Thus through the 
dilution effect of higher turgidity the measures of the concentration of 
solutes might be lower in the second series. 
It is quite conceivable that the rapidly developing bolls made much 
higher demands upon the solutes of the leaf tissue fluids in the second 
period than in the first and that the lower values of both the osmotic 
concentration and specific electrical conductivity in the second period 
may have been due primarily to the withdrawal of solutes from the leaf 
by the developing fruits. 
It is obviously impossible to determine with certainty which of these 
suggested hypotheses is the more logical, or what other explanation may 
be the true one, without special investigation. It is worth while to note, 
however, that the decrease in hydrogen-ion concentration can hardly be 
explained by the simple assumption of relatively higher turgidity in the 
second series of determinations. The organic acids are in general so 
weakly ionized that dilution has but little influence on the concentration 
of the hydrogen-ion. Since dilution is a highly improbable explanation 
of the change in the hydrogen-ion concentration, it can hardly be assumed 
to be the most probable explanation of changes in the value of A and k. 
Some light may perhaps be thrown upon the problem by considering 
in a comparative way the percentage difference between the first and 
second series. 
A comparison of the percentage changes in Egyptian and Upland 
cotton as given in Table XIX shows that the decrease in the concentra¬ 
tion of total solutes and of electrolytes from the first to the second series 
of determinations is greater in the Upland than in the Egyptian cotton. 
The average value of the change in freezing-point depression, A, is 6.16 
per cent in Egyptian and 10.03 P er cent m Upland cotton. The average 
change in specific electrical conductivity, k , is 7.14 in Egyptian and 
11.82 in Upland cotton. This result has an important bearing upon the 
suggested hypothesis that the decrease in osmotic concentration and 
electrical conductivity from the first to the second series of determina¬ 
tions is due to the rapid withdrawal of solutes from the leaves by the 
developing bolls. If the factor of the withdrawal of solutes by the de¬ 
veloping bolls is important enough to account for the decrease in the 
concentrations of total solutes and electrolytes from the first to the sec¬ 
ond series, it might reasonably be expected to account for certain of the 
differences between the various kinds of plants. We have no quantita¬ 
tive measure of the relative number of developing bolls in the various 
series of plants in the first and second series, but the general impression 
derived from an inspection of the two types of cotton in the field is that 
at the time of the first series of determinations the Upland plants had 
relatively more well developed bolls than the Egyptian plants, while by 
the time the second series of determination was made, the slower-devel¬ 
oping Egyptian cotton had produced a more nearly comparable crop of 
fruits. 
74024 — 24 - 
