56 WEEVIL-RESISTING ADAPTATIONS OF COTTON. 



though the weevils be successfully resisted. Such injured bolls often 

 show a brownish discoloration of the interior tissues near the base 

 and connecting with the nectaries, which may indicate a bacterial 

 disease, to be discussed later. Sometimes this affects the walls only, 

 sometimes one or more seeds and the surrounding lint. 



THICK-WALLED BOLLS. 



In the Kekchi cotton there are considerable variations in the thick- 

 ness of the outer wall of the boll. Xot infrequently the wall equals 

 or exceeds the length of a weevil's snout, so that only the largest or 

 longest snouted weevils would be able to make an opening into the 

 interior cavity. It was noted, also, that on the inside such bolls are 

 often quite free from these injuries or small larva?, though numerous 

 attempts may have been made. Large larvae or pupse may be found, 

 but these have come, obviously, from eggs laid while the boll was still 

 young. On some plants the development of large thick walls takes 

 place very promptly, so that a protective character of considerable 

 value might be obtained if this feature could be increased and ren- 

 dered constant. Early development of the thick walls was indicated 

 by the fact that the young seeds and lint did not fill the cavity, and 

 the seeds were still far from mature. Instances might be drawn 

 from other plants where the growth of the pod or seed vessels far 

 outruns the seeds at first, so that the development of such a character 

 in cotton might reasonably be expected. 



Even when a wall thicker than usual has been bored through, the 

 egg must be laid on the outside of the mass of lint which still inter- 

 venes between it and the young seed, so that the larva's chances of 

 development are greatly lessened. As will be shown later in the dis- 

 cussion of proliferation in the bolls, the instances are very numerous 

 in which, although the wall is penetrated, no further damage results ; 

 either the egg is not laid or the development of the larva is pre- 

 vented by proliferation. In any event the boll escapes further 

 injury, and it is a very significant fact that in the dissection of a large 

 number of such bolls of Kekchi cotton scarcely any young larva? 

 were found, in spite of the fact that most of them had been punctured 

 not once only, but many times. 



TOUGH LININGS OF CHAMBERS OF BOLLS. 



The three, four, or five chambers which contain the locks of cotton 

 in the unopened boll have each a complete membranous lining. In 

 the Kekchi cotton, at least, this is extremely tough and parchment- 

 like, even in bolls not yet full grown and in which the seeds are not 

 yet fully formed. This membrane is readily separable from the 

 more fleshy external layers of the boll, and though flexible, it is very 



