SECTION III : WEEVIL RESISTANT COTTONS 243 



that in the plateau region of Mexico the long dry season effectually Mexican 

 excludes the weevil, so that varieties of cotton from the Mexican co 

 highlands, instead of being weevil-proof, as sometimes represented, 

 may have no immunity whatever when brought into the much more 

 moist climate of the cotton belt of the United States ' (I.e. p. 10). 



' It is not improbable that the Upland varieties previously known 

 in the United States came originally from the more or less arid 

 regions of Mexico, where absence or very small development of the 

 basal branches keeps the ground from being constantly shaded and 

 gives better chances for the weevils to be killed by the drying out of 

 the fallen squares.' 



1 Our Upland cottons are undoubtedly of American origin, but the 

 region from which they came has not been ascertained. Some of 

 the Texas varieties are said to have been brought from Mexico. 

 Coronado's Journal of the earliest Spanish exploration in Arizona 

 and New Mexico contains many references to the cultivation of cotton 

 by the Indians. There can be little doubt that the agricultural Indians 

 of the Gulf region also cultivated cotton, though no documentary 

 evidence of the fact seems to have come to light as yet.' 



' It is highly probable that the original home of the cotton plant, Boll 

 and of the boll-weevil as well, was in a somewhat arid region, since 

 it is only under such conditions that the weevil would be effectually 

 prevented from increasing to the fatal degree of destroying its host 

 plant, and thus cutting off its only means of subsistence. On the 

 other hand, it was only in a humid country like Eastern Guatemala 

 that many of the weevil-resisting adaptations would be likely to 

 develop if, as now appears, it has required the selective influence of 

 the boll-weevil itself to bring them to their present advanced 

 development.' 



' The adaptive character of this habit of shedding the parasitized 

 squares seems to be confirmed by the fact that it depends upon the 

 existence of a special layer of soft cells which readily break down 

 when the bud is injured. Many plants have such cells as a means 

 of shedding their fruits, but they seem not to be prevalent among the 

 relatives of the cotton. The cotton itself does not drop the ripe 

 bolls, and even the empty shell often remains long after the seeds 

 are gone. The drier the climate the more effective is the prompt 

 shedding of injured squares ' (I.e. pp. 44-5). 



Mr. Cook shows the plant (Plate n., ff. 1 & 2) with leaves ovate 

 entire below, 3-lobed near the middle and 5-lobed near the top; 



R2 



