INHERITANCE OF FRUIT SHAPE IN 
CUCURBITA PEPO. I 
EpmMuND W, SINNOTT 
(WITH THREE FIGURES) 
During the past few years much progress has been made in our 
knowledge of the inheritance of quantitative characters. We know 
much less, however, about the factors which control the interrela- 
tionships between these various size characters, and which thus 
determine the shape of the organism. The present paper is a pre- 
liminary report on some investigations dealing with certain phases 
of shape inheritance in the summer squash. 
For the past six seasons the writer has been carrying on some 
breeding work with a number of the common types of Cucurbita 
Pepo. Commercial material of this species is apt to be very much 
hybridized and consequently to yield a remarkable variety of forms. 
Many strains are also self-sterile, or become so after a year or two of 
inbreeding. A considerable variety of types was obtained from 
four leading seed firms in the spring of 1916, and an attempt was 
made, by persistent self-fertilization, to establish from this highly 
heterozygous material types which would be essentially pure. Of 
course the majority of plants refused to set seed under these 
conditions, but about twenty-five were found which were self-fertile, 
and the offspring of these (except for a number of lines which have 
since been lost through sterility) have been continuously inbred for 
six generations. In most cases sterility disappeared by the fourth 
generation, and by this time such a high degree of uniformity was 
shown in all plant characters as to make it clear that a fairly close 
approach to homozygosity had been attained. In 1919 a number 
of crosses involving all the more notable character differences were 
made among these various pure types, and the uniformity of the F, 
in every case gave further assurance that the parent types were 
approximately pure. An F, generation from each of these crosses 
was made during the past season (1921). 
95) [Botanical Gazette, vol. 74 
