268 Journal of Agricultural Research voi. xxvii, no. s 
that the properties of the tissue fluids of crop plants may be of importance 
in determining the possibility of their growth and productiveness under 
the varying soil and atmospheric conditions of different regions. 
This assumption (which receives additional support from the work 
which has been done on native vegetation as an indicator of the suita¬ 
bility of land for crop production, as developed by Shantz (49), by 
Kearney, Briggs, Shantz, McLane, and Piemeisel (41), and by Clements 
(11) seems so reasonable that it becomes of the greatest importance to 
determine to what extent species and varieties which are of agricultural 
and horticultural importance are differentiated with respect to the 
physicochemical properties of their tissue fluids, and to ascertain in how 
far observed differences in these properties represent innate and rela¬ 
tively constant differences and to what degree they are the resultant of 
varying environment conditions, such as dryness and salinity of soil, 
insolation, and the evaporating power of the air. 
From the beginning of these investigations 3 we also foresaw the pos¬ 
sibilities of a consideration of the relation of the physicochemical prop¬ 
erties of the plant tissue fluids to the relative vigor of hybrid and parental 
forms and to other problems in genetics. For the past several years we 
have, therefore, been seeking the materials and opportunities for an 
investigation of the physicochemical properties of the tissue fluids of 
heterozygous individuals as compared with those which are homozygous 
for one or many characters. It seemed desirable if possible to obtain 
parent forms which themselves differed in respect to such tissue-fluid 
properties as osmotic concentration, specific electrical conductivity, and 
hydrogen-ion concentration. 
Cotton as grown in Arizona and California is of interest to the physiolo¬ 
gist because it is of necessity grown on irrigated land where the salt 
content of the soil may be relatively high and because it is a plant with 
heavy and watery foliage, which must nevertheless be grown under the 
conditions of temperature and insolation of a fairly severe desert climate. 
Both of these factors—economic importance and peculiar conditions of 
growth—combine to render of special importance the investigation of 
any physiological peculiarities of the plant which may influence its 
capacity for growdh under the rigorous conditions of the Southwest. 
HISTORICAL 
The earlier literature of Egyptian cotton as grown in Egypt has been 
summarized, or at least cited, by Balls (4), who has more recently con¬ 
sidered certain problems of growth and yield (7). We make no attempt 
in this place to review the purely agronomic literature on American 
cultivation of Egyptian cotton, much of which is cited in a paper de¬ 
scribing the American-Egyptian cotton industry, by Scofield, Kearney, 
Brand, Cook, and Swingle (47). Mention should be made also of the 
recent investigations of King (43) on water-stress behavior of Pima 
3 In 1920, Dr. T. H. Kearney, physiologist in charge of alkali and drought-resistant plant investigations, 
Bureau of Plant Industry, and Mr. G. N. Collins, botanist in charge of biophysical investigations, Bureau 
of Plant Industry, recognizing the possible agricultural bearing of the results already obtained from the 
studies of native vegetation, invited us to undertake investigations on the physicochemical properties of 
native indicator plants and of crop plants in the arid West. 
These field operations have included studies on the native vegetation of Tooele Valley, Utah, of cereals 
grown under dry farm agriculture at Nephi, Utah, and on Egyptian and Upland cotton grown under irri¬ 
gation at Sacaton, Ariz. While all these studies in the arid West are mutually supplementary, and should 
be considered in their entirety, they must be presented in sections. The present paper deals exclusively 
with a comparison of Egyptian and Upland cotton and their F] hybrid. 
