JAN. 4, 1921 kempton: linkage in maize 13 



Conclusions. — The cold cake from the sodium carbonate 

 fusion is freed very readily and completely from a palau crucible, 

 much more readily than from one of iridium-platinum, and still 

 more so than from one of pure platinum. The average loss in 

 weight after each sodium carbonate fusion for the palau crucible 

 investigated was about 0.2 mg., and that of an iridium-platinum 

 crucible was about 0.5 mg. The greater average loss of the latter 

 may be ascribed, in part, to volatilization of iridium. 



GENETICS. — Linkage between hrachytic culms and pericarp 

 and cob color in maize.^ J. H. KempTon, Bureau of Plant 

 Industry, U. S. Department of Agriculture. (Communi- 

 cated by G. N. Collins). 



Characters which tend to be inherited together are said to be 

 linked, on the assumption that the genes for such characters are 

 arranged in a linear series on the same chromosome. The agree- 

 ment between the number of groups of linked characters and 

 the number of chromosomes and the linear arrangement of the 

 genes has been demonstrated genetically with remarkable detail 

 for the fruit fly (Drosophila melanogaster) by Morgan and his co- 

 workers and for other species of Drosophila by Metz. 



While it seems almost certain that groups of linked char- 

 acters corresponding to the number of chromosomes will be 

 found also in plants, nevertheless, up to the present time this 

 has not been demonstrated. 



In several respects plants would seem to offer better oppor- 

 tunities than animals for studies of this kind, and among plants 

 Zea mays has many advantages. In the number and frequency 

 of variations alone Zea probably exceeds Drosophila, while in 

 the physiological importance of the structures involved it far 

 surpasses any animal organism where much less fundamental 

 changes are almost certain to be fatal. The number of chromo- 

 somes, however, is relatively large, necessitating the intensive 

 study of many characters, but with each succeeding linkage or 

 demonstrated independence progress becomes more rapid. 



^ Received November 11, 1920. 



