WHITE: INHERITANCE STUDIES ON CASTOR BEANS 515 



Red blush X mahogany and reciprocal gives rose or carmine- 

 stemmed plants in Fi, and approximately i red blush: 2 rose: i 

 mahogany in F2, the actual figures being 47 red blush: 144 rose: 

 47 mahogany, theoretically expected 59.5 red blush: 119 rose: 59.5 

 mahogany. No F3 generation of this cross has been grown, but from 

 the above ratio the plants with rose-colored stems are expected to 

 produce all three F2 types again, while the other two types are ex- 

 pected to breed true. 



As previously stated, there are forms with rose-colored stems that 

 breed true. These when crossed with red blush varieties give all 

 rose-stemmed Fi plants, indistinguishable from their rose-stemmed 

 parent. In F2, these produced 429 rose: 145 red blush, the the- 

 oretically expected proportions being 430.5 rose: 143.5 red blush. 



Associated with the types of stem coloring are pigmented areas 

 in other parts of the plant. The mahogany-red-stemmed plants have 

 mahogany-red leaves and fruits. The rose- and red-blush-stemmed 

 types have green leaves with red or reddish-green midribs. The dark 

 purplish-red- (mahogany bloom) stemmed plants have dark purplish- 

 red leaves and fruits. Plate XXIII is a much enlarged micro-photo- 

 graph in natural colors showing the pattern and distribution of the 

 pigmented areas in the leaf of the mahogany type. The pattern 

 resembles one of the mottling patterns in castor-bean seed coats, and 

 possibly may be due to the same cause. It occurs only in the forms 

 with dark red or purplish-red leaves and stems, and may be regarded 

 as resulting from the absence of the pattern restriction factor previ- 

 ously mentioned. 



Bloom 



Bloom, similar in appearance to that on grapes, in castor beans 

 consists of a scale-like waxy substance, which, under the microscope, 

 resembles a piece of cracked frozen ground. It is easily rubbed off. 

 This covers the whole plant and is especially noticeable on the stems 

 and fruit capsules. In some varieties, it is produced more freely than 

 in others. Many forms are known which breed true to its absence. 

 When it occurs on plants with mahogany stems, a dark purple or 

 purplish-black effect is produced (see Fig. D, Plate XXIV). 



Crosses of bloom X no-bloom give either complete or partial domi- 

 nance of bloom in Fi. In F2, approximately 3 with bloom: i no- 

 bloom were obtained (actual numbers being 1,108 bloom: 377 no- 

 bloom, the theoretically expected being 1,113 bloom: 371 no-bloom). 

 InFs, seeds from unguarded F2 plants without bloom produced only 

 plants without bloom. Seeds from unguarded F2 plants with bloom 

 either bred true in F3 or gave 3 bloom: i no-bloom families. In one 



