9 2i] HARRIS PHASEOLUS 161 



Summary 



This paper presents the results of an investigation of green 

 veight, dry weight, and of the ratio of green weight to dry weight in 

 Drimordial leaf tissue in mutant and parental races of Phaseolus 

 rulgaris. The data show that when grown under as nearly identical 

 xmditions as possible the primordial leaves of the mutant (tetra- 

 :otyledonous) show a smaller green weight, a smaller dry weight, 

 ind a lower ratio of dry weight to green weight than those of the 

 normal (dicotyledonous) parental race. Thus the tetracotyle- 

 donous race is distinguished not merely by striking morphological 

 differences, but by physiological differentiation as well. In this 

 respect the results for the heritable mutant race are in agreement 

 with those for variant individuals within the same strain. 



STATION FOR EXPERIMENTAL EVOLUTION 

 COLD SPRING HARBOR, N.Y. 



