INHERITANCE STUDIES ON CASTOR BEANS 
ORLAND E. WHITE 
Brooklyn Botanic Garden 
Ricinus, though a monotypic genus involving only a single widely 
recognized species (R. communis), possesses a multitudinous number 
of forms, which from time to time have been temporarily ranked as 
species. These forms breed true to many of the numerous characters 
which distinguish them, as shown by data obtained from growing 
several generations of fifty or more types in the experimental breeding 
plots of the Brooklyn Botanic Garden. Numerous crosses between 
even the most extreme types have given perfectly fertile F; and F, 
generation hybrids. 
Hybridization studies to determine the manner of inheritance of a 
dozen or more of these characters have been followed through the 
F,, F2, and, in some cases, the F3 generations. Several thousand 
plants were involved in these studies. 
MATERIALS AND METHODS 
Seeds of the various types were secured through Farquhar & Co. 
of Boston, P. Henderson & Co. of New York City, and from various 
botanic gardens. Many of these types are known in seedsmen’s 
catalogues as varieties or sub-species, and these, much to my surprise 
(since the castor-oil plant is monoecious and wind-pollinated), bred 
true immediately to many of their more prominent characteristics, 
such as stem color, seed color and color pattern, and height. Further 
observations on plants of different varieties grown close together 
demonstrated that very little cross-fertilization took place (certainly 
not more than five percent), even when conditions were most favor- 
able. This rather unexpected tendency to self-fertilization in a 
monoecious plant adapted apparently to wind-pollination is largely 
due to the slightly earlier maturity of the male flowers and to the 
comparative isolation of the flowers of each plant through the preven- 
tion of air currents by the large leaf surfaces. As the stigmatic surfaces 
of the female flowers become exposed and mature, the pollen from flow- 
ers on the same plant has already fallen or falls upon them in small 
clouds, thus insuring, to a large extent, self-fertilization. 
Difficulty is experienced under Long Island climatic conditions in 
making bagged inflorescences on outdoor cultures, set a normal amount 
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