MUTATIVE REVERSIONS IN COTTON. 5 



shorter lobes of the leaves, the i^alor green color, aad the thinner 

 texture. Two or three of the calyx lobes of the Hindi cotton are 

 usually drawn out into a long, slender tootii, a peculiarity previously 

 observed only among the Central American cottons. Mr. Rowland 

 M. Meade has found that the lobes of the calyx of the Hindi cotton 

 are sometimes three-toothed, as also occurs in the Rubelzul cotton, 

 a perennial Upland type from eastern Guatemala with long, pointed, 

 Egyptian-like bolls. The bolls of the Plindi cotton have a rounded 

 coiiic form and are abruptly apiculate. The surface is smooth and 

 even, with the oil glands deeply buried in the tissues, another tendency 

 shared with several of the Central American Upland cottons." 



The agreement of the Hindi with the Central American types of 

 cotton extends even to the frequent display of two types of foHage 

 among unacclimatized plants. Both types yield occasionally large, 

 luxuriant, sterile, or late-maturing plants with deeply channeled 

 five-Iobed and sev«n-lobed leaves. Smaller and more fertile plants 

 have the leaves more nearly plane, with only the usual three lobes 

 regularly develoi)ed. Very vigorous Hindi-like plants often have 

 the same general appearance as Egyptian-Upland hybrids and may 

 represent hybrids between the Egyptian cotton and the extreme 

 form of the Hindi. The large size may be connected with the fact 

 that characters of both of the parent types are brought into ex- 

 ])ression. No tendency to unusual luxuriance appears in Egyptian- 

 Upland hybrids that show the characters of only one of the parent 

 types. The unusual vigor appears to be a physiological phenomenon 

 in some way connected with the tension or conflict in the expression 

 of the divergent charactei-s rather than a consequence of sterility. 

 The abnormal vegetative vigor begins to be manifested in the earlier 

 stages of growth, before any of the plants have reached bearing age.** 



The close similarities of the variant forms of the many different 

 kinds of cotton may be taken to indicate that ancestral characteristics 

 are returning to expression. Otherwise it would need to be assumed 

 that the many different kinds of cotton are engaged in the formation 

 of closely parallel series of new species. Wliether the cotton varia- 

 tions be looked ui)on as mutations or n^t, it is equally desirable to 

 recognize their relation to reversions. It might be as proper to call 

 them revertive mutations as mutative reversions, except that the 

 itlea of reversion is older and better established than that of new 

 species or new characters originating by mutation. 



The range oiancestral diversities that may be expected to reappear 

 in reversions must be learned bv the studv of the wild relatives of 



a Origin of the Hindi Cotton. Circular 42, Bureau of Plant Industry, U. S. Dept. 

 of Agriculture. 1909. 



bThe Vegetative Vigf)r of Hybrids and Mutations. Proceedings, Biological Society 

 of Wa.shington, vol. 17, 1904, pp. 83-90. 

 rcir. 53] 



