A Genetic Study of Plant Height in Phaseolus Vulgaris. 57 
seen in crosses between tall and dwarf (pole and bush) beans 
whether the difference in height of the parents is very great or 
only medium. 
Evidence has been presented in this paper to show that very 
tall and very dwarf beans (pole and bush beans) differ by a 
single fully dominant genetic factor for habit of growth. Pole 
beans are indeterminate in habit, growth continuing apparently 
as long as conditions are favorable. Bush beans are determinate 
in growth, the main axis being terminated by the inflorescence. 
One genetic factor for growth habit differentiates a very tall 
pole bean from a very dwarf bush bean just as sharply as it does 
a medium short pole bean from a medium tall bush bean. 
Evidence has also been presented to show that height of plant 
in beans is influenced by other genetic factors independent of 
habit of growth. These factors have to do with number of 
internodes and with internode length. It has been shown that 
pole-bean races, equally indeterminate in habit of growth, may 
differ considerably in the number of internodes ultimately pro- 
duced and also in the length of particular internodes and the 
mean length of all internodes. Bush beans also differ much in 
internode length and somewhat in number of internodes. Tho 
the evidence presented here is not all that might be desired, it 
is believed to be sufficient to show that both internode length 
and number of internodes in beans are inherited in the same way 
that most quantitative characters in plants are. An intermediate 
development in Fi (often masked by the increased vigor of heterozy- 
gosis), increased variation in F2, and the isolation of distinct 
types in later generations have been shown. The fact that the 
F2 generation of some crosses was not more variable than one or 
other of the parent races — whether or not this be due to irregular- 
ities discoverable in the parent races — cannot displace the positive 
evidence of increased variation in other crosses. 
It seems clear that, if the production of types unlike either 
parent in number of internodes or in internode length is due to a 
segregation of independent, nondominant factors for number of 
internodes or internode length in crosses between two unlike 
bush beans or in crosses between two unlike pole beans, then, 
a similar result must be interpreted in the same way in case of 
crosses between a pole bean and a bush bean. 
From a cross between a tall pole bean and a short bush bean, 
there resulted in F2 a distinct segregation into approximately 
three pole beans to one bush bean. Evidently there existed 
between the parents a single-factor difference for habit of growth. 
But while these pole-bean segregates were all indeterminate in 
habit of growth some of them were much shorter than the pole- 
