July is, 1914 
Mutation in Egyptian Cotton 
291 
In that year two among the progeny rows were totally different in 
type from the parent variety and from one another. The characters of 
each were uniformly expressed in all plants of the row, 1 except the few 
and very different individuals which were obviously first-generation 
hybrids of Egyptian with Upland cotton. These two rows gave rise to 
the Yuma and Somerton varieties, described in an earlier publication 
(Kearney, 1910). Since both varieties appeared suddenly and were very 
uniform from the beginning when protected from cross-pollination with 
other types, the conclusion seems warranted that they were of muta¬ 
tional origin. 
The Yuma variety was subjected during several years to yield tests 
and to mill tests, which showed the variety to be satisfactory in pro¬ 
ductiveness and in the spinning quality of the fiber. When a sufficient 
supply of pure seed had been obtained by carefully roguing the fields 
during three successive seasons, it was distributed to farmers in the Salt 
River Valley, Arizona, where this variety is now being grown on a com¬ 
mercial scale. 2 
Although the Somerton variety produced excellent fiber it was dis¬ 
carded because of its lateness in maturing and the excessive development 
of the vegetative branches. 
Two other varieties, believed to be also of mutational origin, have 
since been developed in Arizona. They are here described under the 
names “Pima” and “Gila.” 
The contrasting characters of the Yuma, Pima, and Gila varieties are 
summarized in Table I. 
Table I.— Characters which distinguish the Yuma , Pima , and Gila varieties of Egyptian 
cotton 
Variety. 
Character. 
Yuma. 
Pima. 
Gila. 
Vege t a t i v e 
Targe, developing rapidly 
Small, developing slowly or 
Smaller than in the Yuma 
branches. 
(PI. XVIII, fig. 1). 
entirely wanting (PI. 
XVIII, fig. 2). 
variety and developing less 
rapidly (Pi. XVIII, fig. 3). 
Reaves of 
A large proportion 5-lobed 
Usually deeply 5-lobed (PI. 
Usually 3-lobed, when 5- 
main stem. 
(PI. XIX). 
XX). 
lobed the basal lobes in¬ 
conspicuous (PI. XXI). 
Involucres.... 
Bracts usually much longer 
than wide, strongly con¬ 
nate (PI. XXII, fig. 2). 
Bracts not much longer than 
wide, separate or nearly so 
(PI. XXIII, fig. 1). 
Bracts not much longer than 
wide, separate or nearly so 
(PI. XXIII, fig. 2). 
Bolls. 
About twice as long as wide, 
tapering from near the 
base, not sharply pointed, 
deeply pitted (PI. XXIV, 
fig. 2). 
Nearly twice as long as wide, 
less tapering and more 
sharply pointed than in 
Yuma, shallow pitted (PI. 
XXIV, fig. 3). 
Considerably less than twice 
as long as wide, abruptly 
contracted at the blunt 
apex, deeply pitted (Pi. 
XXV, fig. 2). 
Average 
length of 
fiber. 
About 1 Yt inches. 
to inches. 
About i-fV inches. 
1 Some of the distinctive characters of each type were noted in the parent individual of the preceding 
year, but in neither case was it then recognized that a complete change of expression had taken place. 
Differences which seem very pronounced when expressed in the 50 or more plants of a progeny row may 
easily be overlooked in a single individual. 
5 The crop of 1913 amounted to about 2,100 bales, and about 15,000 acres were planted in 1914. 
