Feb. 15. 11)15 



Brachysm 399 



the direction of clustering is generally inferior to that of adjacent non- 

 cluster plants. This may be due to the fact already noted, the greater 

 susceptibility of cluster plants to unfavorable conditions, owing to their 

 restricted vegetative development. Occasional exceptions have been 

 noticed, where cluster plants produced lint as good or better than that 

 of nonchister neighbors, but there can he no doubt that the general 

 tendency is in the direction of inferiority of lint. 



CONCLUSIONS 



Brachysm is a term proposed to designate the shortening of the vege- 

 tative intemodes of plants. It is a hereditary abnormality, indicating 

 degeneracy, that has appeared in independent mutative variations in 

 many distinct families of plants, including many cultivated forms. 

 Brachytic variations are of frequent occurrence in cotton, giving rise to 

 the so-called "cluster" and "limbless" varieties, and afford unusually 

 favorable opportunities for learning the nature and physiological sig- 

 nificance of such variations. 



The shortening of the intemodes of the cotton plant is usually con- 

 fined to the fruiting branches without affecting the main stalk or the 

 vegetative branches. JBrachytic variations occur independently in 

 different species and varieties of cotton and do not constitute a natural 

 group with a common origin. 



Brachytic varieties of cotton usually show other abnormaUties of the 

 intemodes, leaves, and involucral bracts. There is also an increased 

 tendency to abortion of the floral buds, and the blasted buds often 

 remain attached to the plant, because of the absence of well-differentiated 

 absciss-layer at the base of the pedicel. 



Though brachytic variations arise by mutative changes in the expression 

 of the characters and show alternative Mendelian forms of inheritance, 

 they afford no additional support to the general theories of mutation and 

 Mendelism as explaining evolution. Such variations represent reduced 

 specialization or intermediate expression of characters and are degen- 

 erative in nature. They are not to be considered as examples of normal 

 heredity or of the evolution of new characters. The abnormalities of 

 brachytic variations are analogous to those found among hybrids and 

 are likewise accompanied by tendencies to sterility or abortion of buds. 



Brachysm is to be associated with other fonns of intermediate expres- 

 sion of characters, representing a general class of metaphanic variations. 

 A more defmite recognition of this class of variations is desirable in con- 

 nection witli the investigation of general problems of heredity and 

 evolution. 



The agricultural value of brachytic varieties of cotton is impaired bv 

 the tendency to abnormal variations and sterility and also by the fact 

 that the cluster cottons arc more severely affected by unfavorable con- 

 ditions. Hence, brachysm is to be avoided in the breeding of superior 

 varieties of cotton. 



