RELATION OF PARALLELTSM TO CLASSIFICATION. 29 



chjui<j;c ol" churju'tors iniist be considered as the production ol" a new 

 elenientaiy species. 



Mutative departures of occasional individuals from the characters 

 of the parent stock are not uncommon in cotton, and differences in 

 the forms of the leaves are one of the most readily distin<i:;uishable 

 types of variation. Most of the variations that produce small bolls 

 can be recoj^nized in advance by their smaller and narrower leaves, 

 or by other (Hlferences of vegetative characters.^ 



RELATION OF PARALLELISM TO CLASSIFICATION. 



The importance of recognizing the fact of a general parallelism of 

 variation in leaf form running through the different types of cotton 

 and related plants is shown also in the field of classification. The 

 genus Gossypium contains a large number of locally different foi-ms 

 of cultivated cotton, as well as numerous wild types. The classi- 

 fication of these into species and varieties is a difTicult task of sys- 

 tematic botany. Failure to recognize the parallelism of variations 

 has allowed the possession of narrow leaves to be taken as a sufficient 

 proof of relationship. Narrow-leaved forms that are probably qidte 

 unrelated have been associated in the same species, while broad and 

 narrow leaved forms of the same type of cotton have been treated as 

 distinct species. These difficulties are well illustrated in a most elab- 

 orate monograph on the classification of cotton by Sir George Watt. 

 The okra-leaved variations of American Upland cotton are repeatedly 

 referred to in this work and add not a little to the complexities of 

 the system of classification. Indeed, they are treated quite differ- 

 ently in different parts of the book and are even assigned to different 

 botanical species. 



The first suggestion is that the American okra-leaved forms repre- 

 sent a variety of an Asiatic species, Gossypium arhoreum. This 

 variety is alleged to have been introduced into North America at an 

 early date and afterwards discarded from cultivation, as the following 

 statements will show: 



It was not until well into the seventeenth century that we possessed any trust- 

 worthy evidence of the Asiatic cottons having been carried to the New World. The 

 Levant cotton (G. herbaceum) was the first to be taken to the United States and grown 

 in Virginia. The Indian cottons (G. obtusifolium, various races) were conveyed to 

 the States by the East India Co., and the Chinese and Siamese cotton (G. nanking) 

 was carried by the French colonists to Louisiana about 1758. G. arhoreum proper 

 does not seem to have been successfully acclimatized anywhere in the New World, 

 though the most important Asiatic (? hybrid) form derived from that species {G. arho- 

 reum var. neglecta) was early carried to America and the West Indies by the East 

 India Co., and is known in the United States to-day under the name of "Okra " cotton. 



There can thus be no doubt that Indian cottons were at an early date introduced 

 into the West Indies and into the United States of America as well, and therefore 



1 Cook, O. F. Cotton Selection on the Farm by the Characters of the Stalks, Leaves, and Bolls. Circular 

 66, Bureau of Plant Industry, U. S. Dept. of Agriculture, 1910. 

 221 



