UNITED STATES DEPARTMENT OF AGRICULTURE 



% BULLETIN No. 925 



v\8 t v V^ / ifi^ Contribution from the Bureau of Plant Industry ?\J 



SHS WM - A - TAYLOR ' Chief 394k. 



Washington, D. C. 



PROFESSIONAL PAPER 



February 18, 1921 



A BRACHYTIC VARIATION IN MAIZE. 



By J. H. Kempton, Assistant in Crop Acclimatization. 



CONTENTS. 



Page 



Definition of brachysm 1 



Review of the literature 2 



Origin and description of the varia- 

 tion 2 



Inheritance of other brachytic varia- 

 tions 6 



Morphological significance 8 



Associated changes 9 



Agricultural advantages 11 



Page. 

 Inheritance of brachysm in hybrids 



with commercial varieties 14 



Brachytic X Boone 14 



Teratological variations 19 



Ears ending in staminate spikes _ 20 



Brachytic X Hopi 23 



Conclusions 26 



Literature cited 28 



DEFINITION OF BRACHYSM. 



Practically all the organs of maize are subject to profound modifi- 

 cation, with heritable variations the rule rather than the exception. 

 Many of these variations are undesirable abnormalities, and a knowl- 

 edge of their origin and inheritance is of practical importance chiefly 

 as an aid to their elimination. Among the many variations, how- 

 ever, one has appeared which gives promise of becoming of agricul- 

 tural value, since it possesses several highly desirable features ad- 

 vantageous for dry-land and irrigated conditions. 



This variation consists of a shortening of the internocles without a 

 corresponding reduction in their number or in the number and size 

 of other organs. (PI. I.) Variations of this nature are found in 

 many agricultural plants, as, for example, the " bush " varieties of 

 peas, beans, squashes, and tomatoes, and are popularly known as 

 dwarfs. The distinction between this type of dwarfing and that in 

 which many if not all of the organs have suffered a reduction in size 

 has been pointed out by Cook (4), 1 who studied similar variations 

 in cotton and suggested the term brachysm for that type which in- 

 volves a shortening of the internodes only. 



1 Serial numbers in parentheses refer to " Literature cited " at the end of the bulletin. 

 16071 — 21 1 



