70 WEEVIL-EESISTING ADAPTATIONS OF COTTON. 



minate its own host plant by permitting the cotton to produce no 

 seed. Paradoxical as it may at first seem, Ave may, nevertheless, 

 believe that the best conditions for the perpetuation of the Aveevil are 

 those which are not altogether favorable to its unlimited multi- 

 plication. 



CONSCIOUS AND UNCONSCIOUS SELECTION. 



There are two principal ways in which improved varieties of cotton 

 and other cultivated plants come into existence. The first is by sud- 

 den or abrupt changes, or sports; also called mutations, saltations, 

 and discontinuous variations. These are represented in cotton by the 

 occasional appearance of a plant with brown lint, a deeply divided 

 leaves & (okra cotton) or very short branches (cluster cotton). The 

 Guatemalan varieties represent a second type of evolutionary history, 

 in wdiich improvement is accomplished by more gradual progressive 

 change, fostered and accelerated by selection. 



Two forms of selection are commonly recognized, natural and arti- 

 ficial, the latter effected by man, the former by circumstances of the 

 environment. This distinction is of doubtful value in any case, and 

 quite obscures the important point in the evolutionary history of 

 cotton and other plants domesticated by primitive man. It would 

 be much better to think of selection as either conscious or unconscious, 

 and between these two a very practicable difference exists. Conscious 

 selection implies the preservation of individuals having a desired 

 quality in the highest degree, while unconscious selection, whether 

 by man, animals, or inanimate conditions, means merely the rejec- 

 tion of the most unfit, so that ■ the improvement of the species or 

 variety is gradual. Conscious selection acts, of course, much more 



a In Guatemala several tribes of Indians prefer brown cotton, and for certain 

 garments use brown cotton only. Separate plantings of brown cotton are not 

 made in the neighborhood of Secanquim, where our experiment was located, but 

 there were said to be such at Cajabon and Lanquin, only a few leagues away. 

 The Cajabon people have a dark -brown cotton called " canch nok," and a lighter 

 brown called " canni nok." 



On the Pacific slope Mr. William R. Maxon found considerable culture of a 

 brown cotton called " ixcaco." At Antigua a similar brown variety is said to 

 have been grown formerly in considerable quantities, the common name of 

 which is " cuyuscate." It was not learned that any special religious use or 

 significance is attached to brown cotton in Guatemala, as is said to be the case 

 in Peru and in India. 



& Some may be inclined to interpret these as reversions and to argue that the 

 deeply divided involucral leaves may be a reminiscence of an ancestral charac- 

 ter of the cotton. Or it may be that the divisions attained by the involucral 

 leaves represent a tendency of specialization which the remainder of the leaves 

 sometimes share by mutation, in accordance with the principle of translocation 

 of characters recently formulated by Dr. R. G. Leavitt (Contrib. Ames Bot. 

 Lab. No. 3). 



