322 
Journal of Agricultural Research 
Vol. XXVII, No. 5 
August 27. The results for the two series of determinations differ 
slightly but are mutually confirmatory, and substantiate those of pre¬ 
liminary determinations made in 1920. They establish the following 
differences between the tissue fluids of the Egyptian and the Upland 
type of cotton. 
The osmotic concentration of the leaf-tissue fluids is higher in Egyptian 
than in Upland cotton. Thus, in the first series of determinations, the 
freezing-point depressions of the Egyptian plants grown from self-fertilized 
seed average 1.404 as compared with 1.353 * n the associated Meade 
plants grown from self-fertilized seed; the Pima plants grown from bulk 
seed average 1.357 as compared with 1.352 in the associated Meade plants 
grown from bulk seed; the Pima plants grown from bulk seed average 
1.340 as compared with 1.300 in the associated Acala plants grown from 
bulk seed. I11 the second series of determinations the average for Pima 
plants from self-fertilized seed is 1.298 as compared with 1.212 in the 
Meade plants from self-fertilized seed; the average for Pima plants 
from bulk seed is 1.257 as compared with 1.201 for Meade plants from 
bulk seed; the average for Pima plants grown in association with Acala 
is 1.280 as compared with 1.182 in the Acala. While the differences 
are not large, varying from less than 1 per cent to slightly more than 8 
per cent, they are in the main far larger than their probable errors and 
are consistent throughout in indicating a higher osmotic concentration 
in the tissue fluids of the Egyptian cotton. The differences are greater 
in the second series than in the first. 
While these differences are small as compared with those which have 
been demonstrated between the native plant species of humid and those 
of arid regions, they may be of significance in the growth of the plants. 
Critical experiments to determine whether this is the case still remain 
to be made. 
The electrical conductivity of the leaf-tissue fluids of Egyptian cotton 
is significantly higher than that of either of the Upland cottons compared. 
This result is found consistently in each of the series investigated. The 
differences range from 2.93 to 3.77 per cent in the first series and from 
8.19 to 9.22 per cent in the second series. The difference between the two 
cottons is greater in the collections made at the later date, notwithstand¬ 
ing the fact that the actual values of conductivity are lower. 
The higher values of electrical conductivity indicate that the Pima 
Egyptian cotton is capable of taking up from the soil and retaining in 
solution in the tissue fluids larger quantities of conducting electrolytes 
than the Upland cottons considered. 
The ratio of specific electrical conductivity, k , to freezing-point 
depression, A, is in general somewhat higher in Egyptian than in Upland 
cotton. The differences are not, however, large. 
This result suggests that the tissue fluids of the Egyptian cotton con¬ 
tain relatively, as well as absolutely, larger quantities of solutes capable 
of carrying the electric current than those of Upland cotton. 
The reaction of the expressed tissue fluids is acid in both types of cotton. 
The values of P H are lower in Egyptian than in the Upland type. Thus 
acidity, as measured in terms of hydrogen-ion concentration, is greater 
in the Egyptian than in the Upland. In the first series of determinations 
the value of P H is 5.245 in the Pima as compared with 5.346 in the 
associated Meade plants grown from self-fertilized seed; 5.269 in the 
Pima as compared with 5.396 in the associated plants grown from bulk 
