INHERITANCE IN RICINUS COMMUNIS, L. PART I. 



By S. C. HARLAND, D.Sc. (Lond.). 

 Imperial Department of Agriculture for the West Indies. 



Introduction. 



This paper presents data on the mode of inheritance of certain 

 characters in the Castor-oil plant, Ricinus communis, L. As pointed out 

 by White (1918 a), RiciniLS is a good subject for genetic experiments. 

 It exists in a large number of distinct and well marked varieties which 

 readily intercross. The seeds remain viable for several years. Further- 

 more, back-crosses, which are so necessary for the proper study of 

 linkage phenomena, are easily effected. 



The characters which have been studied are : 



1. Bloom. 



2. Spines on the capsule. 



3. Colour of the vegetative parts. 



1. Bloom. 



Varieties of Ricinus are distinguished by the presence or absence on 

 the plant body of a waxy bloom. In varieties with bloom two main 

 tjrpes exist : 



A Bloom on stem, petioles, and capsules. 



B. Bloom on stem, petioles, capsules, and also on the under-surface 

 of the leaf 



In class A one or more sub-types may be recognised, but so far no 

 attention has been given to these. T3rpe A is the only one which has 

 been used in the experiments. 



Previous Investigations. 

 Dr O. E. White (1918b) deals with the mode of inheritance of bloom. 

 He states : 



Crosses of bloom x no-bloom give either complete or partial dominance of bloom 

 in Fi. In F^, approximately 3 with bloom : I no-bloom were obtained (actual 



