Feb. a,1924 
Tissue Fluids in Cotton 
295 
In the second series the signs of all four of the differences (column 8) 
indicate a slightly higher ratio, k/ A, in the Egyptian plants. One of 
the differences is certainly insignificant in comparison with its probable 
error. The others may or may not be significant. 
Finally, the percentage column (10) shows that the differences be¬ 
tween Upland and Egyptian cotton do not exceed 3.3 per cent of the 
value of the constant for the Upland form. 
The net result of this comparison seems to be that, taking the materials 
as a whole, there is no certain evidence of a difference in the relative 
values of k in the two groups of cottons. Such differences as do appear 
are not wholly consistent from series to series and may be due merely 
to the errors of random sampling or to heterogeneity in the field upon 
which the plants were grown. The results for both the first and second 
series of determinations suggest, however, that the ratio is slightly higher 
in Egyptian than in Upland cotton. It will not be worth while to con¬ 
sider this problem further until conductivities can be corrected for the 
viscosity of the fluid, or until comparisons can be based on the actual 
analytical determination of one or more of the electrolyte ions. 
A comparison of the ratio k/A in the first and second series of deter¬ 
minations (Table XII) shows that in both Egyptian (column 5) and 
Upland (column 6) cotton, the ratio is somewhat smaller in the second 
than in the first series. These differences are not sufficiently large in 
comparison with their probable errors to be considered definitely signifi¬ 
cant as individual constants. The consistency of the results evidences 
strongly for a relatively lower concentration of electrolytes in the deter¬ 
minations made later in the season. 
The differences between Egyptian and Upland cotton are apparently 
larger in the second than in the first series. 
COMPARISON ON THE BASIS OP HYDROGEN-ION CONCENTRATION 
While various authors have determined the total acidity of plant tissue 
fluids by titration, we have relatively little information on their actual 
acidity as determined by the systematic use of indicators, and fewer still 
by electrometric methods, giving the true hydrogen-ion concentration. 
Much of the work has been of a wholly incidental nature, and no attempt 
will be made here to review it in detail. Reference may be made to a 
recent summary by Atkins (j). 
Haas (18 , 29), Truog (50), Hoagland ( 34 ), and Atkins (j) have shown 
that, in general, plant saps have a hydrogen-ion concentration well on 
the acid side of neutrality. Our findings for cotton are in agreement 
with this general experience, although the acidities which we have found 
are not so high as those stated by Atkins (r). 
As far as we are aware, detailed studies of the relative values of hydro¬ 
gen ion concentration in agricultural varieties have not been made 
heretofore. 
The constants for the acidity of the tissue fluids of the Egyptian and 
Upland cottons measured in terms of P H appear in Table XIII. 
The average values of P H in the various series of Egyptian cotton 
(column 5) range from 5.24 to 5.41, while in the Upland cotton (column 6) 
they range from 5.30 to 5.46. Thus all averages are well on the acid 
side of neutrality. 
Comparing the Upland and Egyptian cotton by means of the difference 
column (8), we note that the P s values for Egyptian cotton are in all 
cases lower than those for the Upland cottons. 
74024—24-5 
