218 Inheritance in Ricinus communis, L, 



the F2 results. It is hoped to elucidate the relation of the two factors 

 by a series of back-crosses with the double recessive. 



General Summary. 



This paper is concerned with the mode of inheritance of certain 

 characters in the castor-oil plant, Ricinus communis, L. The experi- 

 mental results may be summarised as follows : 



1. The presence of bloom is partially dominant to its absence. 

 Presence and absence of bloom behave as a pair of simple allelomorphic 

 factors. The factor for bloom is denoted by B, and its allelomorph 

 byb. 



2. The presence and absence of spines on the capsule form another 

 pair of allelomorphs, with spininess partially dominant. The factor for 

 spines is denoted by S, and its allelomorph by s. 



3. The experiments on the inheritance of stem colour in the cross 

 green by mahogany indicate that two independently inherited Mende- 

 lian factors are involved : 



M. The factor for mahogany. 



G. The factor for green. 



The four types resulting from the cross Mg x mG are : 



9 MG 3 Mg 3 mG 1 mg 



Rose Mahogany Green Tinged 



4. Experiments on the relation between the different factors show 

 that S and M,S and B, M and G, and perhaps G and B are independently 

 inherited. Factors M and B show repulsion in the cross Mb x mB. 



REFERENCES. 



Grisebach, H. R. A. 1864. Flora of the British West Indies. 



Harland, S. C, " Notes on Castor-oil in the West Indies." Agricultural News, 



Barbados, No. 416, p. 100. 

 White, 0. E. 1918 a. " Breeding New Castor Beans." Journal of Heredity, 



Vol. IX. No. 5, May — June. 

 h. " Inheritance Studies on Castor Beans." Brooklyn Botanic Garden Memoirs, 



I. 513—520. 



