10 MUTATIVE REVERSIONS IX COTTON. 



uniform, perhaps as a result of the stiono: contrast between tiiem 

 and the normal Egyptian plants. 



If the Hindi plants stood alone, they would bo identihed at once 

 as members of a series of Mexican cottons related to our Upland type, 

 but with definite differences. Some of the varieties contain many 

 plants that combine the Egyptian with the Hindi characters, plants 

 tliat may be viewed as ordinary hybrids, but the persistence and 

 remarkable uniformity of the Hindi type can hardly be understood 

 except by the analogy of complete reversions to the Upland type 

 already known in experiments with Egvi^tian-Upland hybrids. 



CONTRASTED CHARACTERS OF COTTON REVERSIONS. 



Though complete reversion may not have been formally recognized 

 as a phenomenon of heredity, it is believed that an examination of 

 related facts will show a very general tendency of reversions to 

 extreme expression of characters rather than to slight or intermediate 

 expression. Even when only one character appears to be changed 

 there is more likely to be a complete change than a partial one. 

 Uniform, deep-red ears are a much more frequent reversion in corn 

 than ears that are pale red or that have only a part of the kernels 

 red. Black lambs are generally black all over, and only very rarely 

 spotted, except upon the head. This remains true even when black 

 males are regularly bred Avith wdiite females, as on the elevated 

 plateaus of Guatemala, where the Indians prefer the black wool. 

 A few piebald sheep were finally seen in one fiock, but only after 

 many of tlie mixed flocks had been looked over in vain. 



Similarly accentuated contrasts are found between the Egyptian 

 cotton and the Hindi. The veins of the leaf of the Hindi cotton are 

 united at the base into a larger and more prominent cushion, or 

 pulvinus, than in the Egyptian cotton, and the pulvinus of the Hindi 

 cotton is rendered the more conspicuous by its red color, which is 

 shared by the upper side of the somewhat swollen end of the petiole, 

 for about half an inch. In normal Egyptian cotton the pulvinus is 

 pale green, like the other portions of the veins, or only slightly tinged 

 with reddish, like the end of the petiole. Under some conditions the 

 stalks and petioles of the Egyptian cotton take on a bright-red color 

 like the pulvinus of the Hindi, but in spite of the reddening of most 

 of the petiole the swollen terminal part and the pulvinus of the 

 Egyptian leaf remain distinctly paler. Exactly those parts that are 

 the most promj^tly and deeply reddened in the Hindi plants are per- 

 sistently paler in the Egyptian. 



The stalks and petioles of the Hindi plants may also redden with 

 age, as in the Egyptian, and when this occurs the contrast of color 

 is destroyed, for the red of the pulvinus and the swollen end of the 



[Cir. 53J 



