520 BROOKLYN BOTANIC GARDEN MEMOIRS 



Heterozygosis 



Fi hybrids between several of the forms produced, as in many 

 maize crosses, a much larger amount of seed than either parent, the 

 environment being practically the same for all. Fi hybrids between 

 still other forms, however, failed to show this increased productivity. 

 This is also true of maize Fi hybrids. 



This increased productiveness in Fi should be, as in the case, of 

 maize and tomatoes, of great commercial value, since crossing castor- 

 bean varieties, where no particularly accurate results are desirable, 

 is very simple and could be done rapidly. Plants of the two types 

 to be crossed could be grown separately and one lot used entirely as a 

 pollenizer. A large quantity of pollen from the same spike matures 

 at the same time. Hence, these spikes could be cut off when nearly 

 mature and laid on paper sheets till the pollen was shed — a matter 

 of a day or two. The pollen could then be collected in a powder 

 gun or similar device and shot over the newly matured pistils each 

 morning. The male flowers on the plants used as seed-bearers, 

 for the most part, can be easily rubbed off without injuring the 

 fiower spike. The amount of selfed seed by this method would be 

 very small, most of the mature seed being crossed. As ordinarily 

 planted commercially, one bushel of beans running 1,500 beans to 

 the pound will plant anywhere from 6 to 40 acres, depending on the 

 distance apart and the number of beans planted per hill (1-3 beans). 

 Some of the commercial varieties run as high as 3,000 beans or more 

 per pound. Castor beans produce from 10 to 40 bushels per acre, 

 depending on the variety, soil, climate and length of frostless season. 

 With these facts in view, it seems unnecessary to urge the commercial 

 importance of using Fi generation hybrid seed produced by the method 

 mentioned above. Experiments to determine which varieties crossed 

 together would give the greatest yields in a given locality should be 

 made in regions where the beans are grown commercially, since, as 

 previously stated, there is great variation in varieties as regards this 

 characteristic. This characteristic of increased productivity in Fi 

 progeny of certain varieties, combined with such characters as "non- 

 popping" and high oil content, should help toward putting castor-bean 

 growing on a better commercial basis in this country. No experiments 

 regarding increasing the oil content through "selection," so far as 

 the writer knows, have been made. Varieties with seed yielding 30 to 

 45 percent oil are said to be already common commercially. Experi- 

 ments with, and chemical analysis of the innumerable varieties would 

 possibly give us strains with a much larger oil content. 



