66 WEEVIL-RESISTING ADAPTATIONS OF COTTON. 



Avise. In a humid tropical country the seeds, if left to themselves, 

 remain inclosed in the tangled mass of lint and usually rot. Birds 

 might carry the lint away to build nests, and in so doing might assist 

 in scattering the seeds, but in most of the varieties the seeds are to 

 be detached only Avith difficulty. 



Composed as it is of nearly pure cellulose, the lint can afford very 

 little .nourishment, even in the younger stages. Between the lint and 

 the watery proliferating tissue the weevil larva must find the inside 

 of a cotton boll a very 'uliospitable place unless it can penetrate to the 

 seeds. Dead and moribund larvse are occasionally foiuid in these 

 unfavorable situations. And evon the seeds themselves do not pro- 

 vide so favorable a food as the pollen, as shown by the nuich longer 

 time required by the larvae to develop in the boll than in the square.. 



PROTECTIVE SEED ARRANGEMENT IN KIDNEY vOTTON. 



Further intimation of the protective value of the lint is to be found 

 in the very peculiar Kidney cottons, so called because the seeds are 

 crowded together in the central angle of the chamber and adhere 

 firmly to each other, thus forming a small, kidney-like mass. This 

 unique arrangement brings all the lint to the outside of the seed, and 

 may be the explanation of the fact that the Kidney cottons are the 

 only representatives of the Sea Island type which have gained a wide 

 distribution on the mainland. The separate-seeded Sea Island cot- 

 tons came from Barbados, where the boll weevil did not exist and has 

 not yet been introduced. (See PI. X, fig. 2.) 



The outer wall of the boll of the Kidney cotton is notably thinner 

 than that of Kekchi cotton, so that the beaks of the weevils could 

 reach through without difficulty. But with the layer of lint to sup- 

 plement it the wall becomes, for practical purposes, much thicker than 

 in the free-seeded varieties. The inner parchment lining is rather 

 tough, though apparently less so than in the Kekchi cotton. 



The Indians about Trece Aguas, Guatemala, are said to recognize 

 the weevils as enemies of the dwarf cotton, but it is the local opinion 

 that the Kidney cotton is proof against them. 



No weevils were found on the two l)ushes of Kidney cotton exam- 

 ined in that locality, but these w^ere single plants growing near Indian 

 houses several miles away from the nearest field culture. In a forest- 

 covered country like this part of Guatemala the luxuriant and 

 tangled vegetation may well impede the flight of such an insect as the 

 weevil. And if it lives, as supposed, only on cotton, its chance of 

 I'eaching a single bush of tree cotton would be very small. That the 

 buds and young bolls of the Kidney cotton are able to offer any abso- 

 lute resistance to the weevil seems very improbable, and the abundance 

 of weevils found on the large tree of Kidnev cotton at Tucuru last 

 year proved that the immunity, if any. is not general. 



