WHITE: INHERITANCE STUDIES ON CASTOR BEANS 517 



presence of B and absence of A, the capsules would be thick and 

 leathery, but non-popping. When both A and B are absent, the 

 capsules would be thin, brittle, and non-popping. On this provisional 

 hypothesis, "non-poppers" of the aB class crossed with those of the 

 Ab class would give all AB or "poppers" in Fi and a 9 : 7 ratio in F2. 

 The two types used in the above-recorded crosses would be represented 

 by the formulae 



AABB = "poppers," 

 aabb = "non-poppers." 



Crosses of these would give a 9 : 7 F2 ratio, such as that actually 

 obtained. 



Seed-coat Colors 



Seed-coat colors in castor beans are white, brownish yellow, 

 various shades of red, gray, brown, and black. With one exception, 

 all forms, so far as the writer knows, have seed coats in which the 

 ground color is modified by one of several mottling patterns, although 

 the mottling patterns are inherited, as in garden beans, independently 

 of the ground color. The nearest approach to a self color in the 

 writer's collection is a black-seeded variety having in some cases very 

 few mottling marks and in others none at all. Efforts have been 

 made to discover a self-colored white-seeded variety, but so far with 

 no success. 



In crosses, chocolate brown is dominant over black, red, white 

 and gray. No F2 data are available from any crosses excepting those 

 of red X brownish gray and its reciprocal. The Fi is brown on a 

 gray background. In F2, segregates of various degrees of redness 

 appear as a minority. By counting all those F2 segregates with a 

 red cast, an approximation to a ratio of 3 brownish gray : i reddish 

 gray is obtained. The actual results are 172 non-red : 40 reddish 

 gray or red, the theoretically expected results being 159 non-reds : 53 

 red gray. No reds as brilliant as the grand parental type appeared, 

 showing that more than a single pair of factors is involved. 



In F3, seed from unbagged F2 light red segregates gave all light 

 reds in the majority of cases. Seed of the same kind from medium 

 red F2 segregates also bred true. Seed from unbagged brown F2 

 segregates gave browns of various shades in some cases in F3, while 

 in others, browns, reds, and brown grays were produced. Reds as 

 brilliant as the red ancestor were secured from red F2 segregates. 



At least three types of seed-coat color mottling can be distinguished 

 definitely in castor-bean seeds. One is coarse-veined, one is fine- 

 veined, dotted and splotched, while the third is characterized by a 

 very few large splotches. When the seed-coat is black, the mottling 



