INHERITANCE STUDIES ON CASTOR BEANS 



ORLAND E. WHITE 



Brooklyn Botanic Gardeyi 



Ricintis, 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 Fi and F2 

 generation hybrids. 



Hybridization studies to determine the manner of inheritance of a 

 dozen or more of these characters have been followed through the 

 Fi, 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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