300 
Journal of Agricultural Research 
Vol. II, No. 4 
Abassi, Yannovitch, Nubari, Sakellaridis, and Assil varieties have suc¬ 
cessively been developed. 
As grown in Arizona from imported seed, most of the Egyptian varie¬ 
ties are readily distinguishable by the habit of the plants and by the char¬ 
acters of the leaves, involucres, and bolls, as well as of the fiber. 
So far as the scanty evidence goes, each of these varieties originated 
with a mutant—i. e., an individual plant which showed an abrupt and 
definite change in the characters expressed. This conclusion is supported 
by the more complete data at hand regarding the history of the varieties 
which have been developed in Arizona. 
Plant-breeding work in Arizona was begun 12 years ago with imported 
seed of the Mit Afifi variety. Persistent selection of the best plants 
caused some improvement in earliness and productiveness and in the 
quality of the fiber, but the progress was not very substantial prior to 
1908, in which year two types very different from the Mit Afifi were 
recognized and isolated. One of these was the Yuma variety, now 
commercially grown in Arizona. This form has continued to express 
its distinctive characters with a high degree of uniformity, notwith¬ 
standing the fact that the parent individual and its immediate progeny 
were not protected against cross-pollination. 
Two additional varieties, described in this paper under the names 
4 ‘Pima" and “Gila,” have lately been developed in Arizona. The 
Pima variety appeared as a single plant of marked individuality in a 
field of Yuma cotton at Sacaton, Ariz., in 1910. Its characters have 
been expressed in its progeny with great uniformity during the three 
subsequent generations. This variety is easily distinguished from the 
parent Yuma variety by its relative limblessness and by the correlated 
retention of the lowest fruiting branches and bolls; by the more uniformly 
deeply 5-lobed leaves; by the shorter, relatively wider, and nearly sep¬ 
arate involucral bracts; by the plumper and more abruptly and sharply 
pointed bolls; and by the longer fiber. 
The Gila variety is derived from a single plant discovered by Mr. E. W. 
Hudson in a field of the acclimatized Mit Afifi stock grown at Sacaton, 
Ariz., in 1908. In its external characters this type resembles the parent 
Mit Afifi variety much more than the Yuma, but differs from the Mit 
Afifi in its earlier ripening, smaller vegetative branches, greater pro¬ 
ductiveness, and longer fiber. The individuality of the parent plant, 
together with the uniformity shown by its progeny during the subse¬ 
quent generations, indicates that the Gila variety, like the Yuma and 
the Pima, is of mutational origin. 
Egyptian cotton exhibits, although in a minor degree, the tendency to 
develop new varieties by mutation which characterizes Oenothera La - 
marckiana. There is a further parallel in the fact that in both cases 
very similar, if not identical, new characters come into expression at 
