35 



culture which are of more or less assistance in resisting or avoid- 

 ing the weevil. 



The large leafy involucre of the cotton may have been at first a 

 protective adaptation, though the weevils later learned to enter it 

 easily. In some of the Guatemalan sorts the bracts are grown 

 together at the base as though the evolution of a closed involucre 

 had begun. The hairy stems assist the ants in climbing, but 

 impede the weevils, and thus increase the chances of capture. 

 Prompt flowering and determinate growth enable an annual 

 variety to ripen more seed. A perennial kidney cotton also 

 escapes extinction by producing nearly all its blossoms at one 

 season. In the central plateau region of Salama and Rabinal 

 another perennial variety is cut back annually to the ground. New 

 shoots spring up and the new crop is set within a short time, while 

 the plants are still small enough to be cared for by the chickens 

 and turkeys. 



Another of these protective adaptations proves to be of such 

 potential significance as to call for announcement in advance of 

 a detailed report. The issue is nothing less than that the cotton 

 plant, in some of its varieties, has finally developed a practical 

 means of resisting and destroying the weevil larvae. The process 

 is in the nature of a varietal characteristic subject to increase by 

 selection. The efficiency of the adaptation is such that a variety 

 in which it appeared uniformly would afford no opportunity for 

 the weevil to breed, and would thus be a means of exterminating 

 it. 



The facts are simple and have been thoroughly established 

 during the department's entomological studies of the weevil for the 

 past decade, but they have not been interpreted as a protective 

 adaptation, nor as a character subject to further selective develop- 

 ment. Messrs. Hunter and Hinds have reported* that in some 

 instances as high as 41 per cent, of the boll-weevil larv^ fail to 

 develop, as a result of what they have termed a ' gelatinization' 

 of the tissues of the young bud or 'square.' 



In the later stages the injured buds often appear as though filled 

 with a structureless exudation, and it was not unnaturally supposed 

 that the abnormality was the result of some disturbance of nutri- 

 tion, or of bacterial infection. The material failed, however, to 

 yield cultures of bacteria or to respond to experiments with 

 fertilizers. The opportunity of examining the earlier stages of the 

 phenomenon show that the conditions are far less abnormal than 

 have been supposed, and that the * gelatinization' is simply the 

 result of very active growth or proliferation of the loose tissue of 

 the tube or column, which in the flowers of the mallow family 

 surrounds the style and bears the stamens. 



The usual programme would be for the young squares to fall to the 

 ground when the larva has hatched and begun to eat out the pollen 

 of the young bud. Proliferation involves the opposite procedure. 



* Bull. 45, Bureau of Entomolojjy, U, S. Dept. Agriculture p. 96, 1904. 



