Feb. 2,1924 
Tissue Fluids in Cotton 
279 
the time of the collection of the different samples influence in a somewhat 
similar manner the sap properties of both Pima and Upland types. The 
standard deviation of the difference between the constants of the two 
species is given by the formula 
<T 2 (i»_t7') = (T 2 j» ± cr 2 u — 2 Tpu <Tp O'er. 
Using this formula, we see that the difference in freezing point lowering 
of the tissue fluids of Egyptian and Upland cotton is 0.1560 ±0.0159. 
This value is 9.8 times as large as its probable error. While the 
number of samples is small it seems clear that, at this particular growth 
stage at least, the osmotic concentration of the leaf-tissue fluids of the 
Egyptian cotton is distinctly greater than that of the Upland. The fact 
that the individual differences are without exception of the same sign is 
a strong evidence for the validity of this conclusion. 
The results for osmotic pressure, P, are stated in Table III. The 
difference in mean osmotic concentration is 1.872 ±0.191 atmospheres. 
Table III .—Statistical constants for osmotic pressure in Pima and Upland cottons 
in 1920 
Pima, P. 
Upland, U. 
Mean.. 
i5.639iO.265 
i. 4 I 9 ±o.i 88 
9.074 
13.767 ±0.269 
i. 437 ±o*I 9 ° 
10.44 
S. D. 
C. V. 
rpv ~ +0.7436 ±0.0836 
The specific electrical conductivities, k, are without exception some¬ 
what higher in Pima than in the varieties of Upland cotton with which 
it is compared. Calculating the statistical constants for electrical con¬ 
ductivity and determining the probable errors by the method above, 
the data presented in Table IV were obtained. The difference in the 
electrical conductivity is 0.00463 ±0.00058, showing that the tissue 
fluids of the Egyptian cotton contain somewhat larger quantities of 
ionized electrolytes than do those of Upland varieties. 
Table IV .—Statistical constants for electrical conductivity in Pima and Upland cottons 
in 1920 
Pima, P. 
Upland, U. 
Mean. 
o.o3596±o.ooi37 
o.oo 733 ±o.ooo 97 
20.39 
o.Q3i33±o.ooii9 
o.oo633±o.ooo84 
20.21 
S. D. 
C. V. 
rpu = ±0.9058 ±0.0336 
Comparing the values of the ratio of electrical conductivity to freezing 
point lowering, k/A, for the 13 pairs of Egyptian and Upland cotton, we 
find that in eight cases the ratio is higher in the Egyptian than in the 
Upland cottons, whereas in five cases the results indicate that the relative 
proportion of conducting electrolytes is lower in the Egyptian than in 
74024—24-4 
