1028 
Journal of Agricultural Research 
Vol. XXXI, No. 11 
varieties were grown from seed which had been rendered more uniform 
by self-fertilization of plants selected as true to type. Three Upland 
varieties—Meade, Acala, and Lone Star—as well as Sea-Island cot¬ 
ton—were introduced in the comparison. 
The exact cultural details neea not be discussed here. The plant¬ 
ings were made in a manner similar to those adopted in earlier 
experiments. This involves the distribution of all of the varieties 
over the field in short subrows or subplots. Samples of mature leaf 
tissue were taken from all of the varieties of a subplot at the same 
time. 
The leaf-tissue fluids were extracted and the physicochemical 
constants determined in a manner described in an earlier paper (« 3 ). 
PRESENTATION AND ANALYSIS OF DATA 
In the presentation of the results only the averages are given. 
Probable errors have been omitted for the following reasons: (a) The 
number of determinations on any one variety is small, and this 
renders the interpretation of the probable errors difficult under any 
conditions, particularly under the conditions of the present experi¬ 
ment; (6) the chief use of the probable errors of the means would have 
been in connection with the determination of the probable errors of 
the differences between any two varieties. 
Such probable errors can be determined only if the correlation 
between the constants for the two varieties under comparison be 
known. The determination of such correlations on the basis of as 
large a number of varieties and as wide a spacing of varieties as are 
found in these experiments presents considerable difficulty. 3 
In the determination of the averages a somewhat different method 
h as p roved to be desirable for the two experiments. 
While the plot utilized in the experiment of 1922 showed great 
irregularities of soil conditions, which were strikingly evident in the 
characteristics of the plants, a fairly uniform stand was obtained for 
the whole plot. 
In the experiment made in 1924 the southern portion of the experi¬ 
mental plot carried a fairly uniform stand, but toward the northern 
end of the field manjr sections produced no plants at all. These 
differences in the salinity and texture of the soil, to which the diver¬ 
sities in stand are due, doubtless play an important part in determin¬ 
ing the physicochemical properties of the plant-tissue fluids. It has 
seemed desirable, therefore, to prepare two sets of averages for the 
determinations made in 1924, the first comprising the southern end 
of the field, where materials could be obtained for all of the varieties, 
and the second including the northern end of the field, the stand 
there being not as good as that on the southern end. These two 
averages, with indications of the number of determinations on which 
these are based, are given as “partial” and “whole” series in the 
tables. 
3 It might seem that these difficulties should have been overcome by a different arrangement of the plant¬ 
ings. This, however, was impossible with the number of varieties involved in the present experiments 
without so reducing the number of plants per subplot that the determinations would have been based on 
tissues from one or but a very few individuals. In the organization of this experiment it seemed best, all 
things considered, to increase the size of the individual cultures, even though this resulted in the separation 
of the groups of plants to be compared. 
