646 Varietäten, Descendenz, Hybriden. 



ving been cultivated in Egypt neariy a Century ago. Whether or 

 not this be true, there can be no question that the varieties now 

 grown are of mixed ancestry, a condition which some investigators 

 regard as favorable to mutation. 



Numerous varieties have appeared from time to time in Egypt. 

 The Ashmuni variety, now grown only in Upper Egypt, originated 

 about 1850. This variety gave rise in 1887 to the Mit Afifi, and 

 from the latter the Abassi, Yannovitch, Nubari, Sakellaridis, 

 and Assil varieties have successively been developed. 



As grown in Arizona from imported seed, most of the Egyp- 

 tian varieties are readily distinguishable by the habit of the plants 

 and by the characters of the leaves, involucres, and bolls, as well 

 of the fiber. 



So far as the scanty evidence goes, each of these varieties ori- 

 ginated with a mutant — i. e., an individual plant which showed an 

 abrupt and definite change in the characters expressed. This con- 

 clusion is supported by the more complete data at band regarding 

 the history of the varieties which have been developed in Arizona. 



Plant-breeding work in Arizona was begun twelve years ago 

 with imported seed of the Mit Afifi variety. Persistent selection 

 of the best plants caused some improvement in earliness and pro- 

 ductiveness and in the quality of the fiber, but the progress was 

 not very substantial prior to 1908, in which year two types verj'- 

 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, notwithstanding the fact that the parent 

 individual and its immediate progenj^ were not protected against 

 cross-pollination. 



Two additional varieties, described in this paper under the 

 names „Pima" and „Gila"; have lately been developed in Arizona. 

 The Pima variety appeared as a Single plant of marked individua- 

 lity in a field of Yuma cotton at Sacaton, Arizona, 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 limbless- 

 ness and by the correlated retention of the lowest fruiting branches 

 and boll; by the more uniformly deeply 5-Iobed leaves; by the 

 shorter, relatively wider, and neariy separate involucral bracls; by 

 the plumper and more abruptlj^ add 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, Arizona, in 1908. In its externa! characters 

 this tvpe resembles the parent Mit Afifi variety much more than 

 the Yuma, but dififers from the Mit Afifi in its earlier ripening, 

 smaller vegetative branches, greater productiveness, and longer 

 fiber. The individualit}'' of the parent plant, together with the uni- 

 formity shown by its progeny during the subsequent 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 ten- 

 dency to develop new varieties by mutation which characterizes 

 Oenothera Lamarckiana. There is a further parallel in the fact that 

 in both cases very similar, if not identical, new characters come 

 into expression at different times and in different places. An example 



