270 
Journal of Agricultural Research 
Vol. XXVII, No. S 
In conclusion, Ball makes the significant suggestion: “Egyptian cotton 
(Gossypium peruvianum) may be classified as a facultative halophyte.’’ 
As far as we are aware the only previous work on the hydrogen-ion 
concentration of the tissue fluids of cotton is the single determination of 
P H 4.6 in leaf, stem, and petal tissue given by Atkins (1). As will be 
shown later, this represents a distinctly higher acidity than that which 
we have found in any instance in the leaf tissue fluids of cotton. 
MATERIALS AND METHODS 
Since we are here dealing with a problem in which every possible source 
of error must be considered, and in as far as possible eliminated, in order 
to secure conclusive results, we shall describe the materials and methods 
employed in some detail. The importance of these details is not, we 
believe, overemphasized. 
A detailed discussion of the Egyptian and Upland types of cotton and 
of their hybrid is not necessary in this place in view of the fact that 
the results of an investigation of the hybrids which has been in progress 
for the past several years have been published (40). The data given 
by Kearney in regard to height of plants and dimensions of the leaves 
were confirmed by measurements made on the material used by the 
writers in their investigations in 1921. It need only be mentioned here 
that the Egyptian and Upland types differ in a large number of mor¬ 
phological characters, the differences being of a kind and degree indi¬ 
cating that they belong to very distinct botanical species. When the 
two types are grown under comparable conditions the Egyptian plant is 
taller and has longer internodes and branches and larger, more deeply 
lobed, thicker, smoother, and darker green leaves than the Upland plant. 
GENETIC NATURE OF THE SEED EMPLOYED, AND CHARACTERISTICS OF THE 
VARIETIES AND OF THEIR Fj HYBRID 
Three varieties of cotton are considered in this paper: Pima represents 
the Egyptian, while Acala and Meade belong to the Upland group of 
cottons. 
The following is the history of the Egyptian and Upland seed employed 
for the special cultures upon which the physicochemical determinations 
were made in 1921. The origin and characteristics of the Pima variety 
have been described by Kearney (57, 40). The “Pima selfed” seed was 
obtained by selfing a number of plants in a progeny designated Pima 
Hi—5 Acala A, which was grown at Sacaton in 1920. This progeny 
was derived, by three generations of controlled self-pollination, from 
progeny Pi-40 of 1917, which had been derived by three generations of 
controlled self-pollination, from plant Pi, selected in 1914. The line of 
descent of Pi-40 has been described elsewhere (38). The “Pima selfed” 
material of this experiment represented, therefore, seven generations of 
strict inbreeding and was presumably approaching homozygosity. 
The origin and characteristics of the Meade variety are described by 
Meloy and Doyle (46 ). 
The “Meade selfed” seed was secured by self-fertilizing a few plants 
of Meade cotton grown at Sacaton in 1920. These were grown from 
seed harvested from experimental plantings in Georgia, conducted 
under the direction of Dr. O. F. Cook, of the Office of Acclimatization 
and Adaptation Investigations of the Bureau of Plant Industry. This 
