1921] HARRIS—PHASEOLUS 161, 
Summary 
This paper presents the results of an investigation of green 
weight, dry weight, and of the ratio of green weight to dry weight in 
primordial leaf tissue in mutant and parental races of Phaseolus 
vulgaris. The data show that when grown under as nearly identical 
conditions as possible the primordial leaves of the mutant (tetra- 
cotyledonous) show a smaller green weight, a smaller dry weight, 
and 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 
Cop Sprinc Harsor, 
