WHITE: INHERITANCE STUDIES ON CASTOR BEANS 519 



different Fi plants of each were practically uniform as to seed size 

 (see Plates XXV, XXVI, and XXVII). 



Most of the large-seeded forms and some of the very small-seeded 

 forms (with indeterminate growth period) require a long season to 

 produce mature seeds, so that even when F2 populations were started 

 in the greenhouse in pots several months before planting out, only 

 about two thirds of the segregates matured seed. One year, attempts 

 to overcome this difficulty by growing the plants in 10 cm. pots for a 

 year were unsuccessful. The difference in seed maturity between the 

 outdoor and these pot-grown plants was very slight. Because of these 

 difficulties, several of the F2 populations shown in Plate XXVII repre- 

 sent only part of the segregates — the small- and intermediate-seeded 

 classes. In F2 populations from small X large seed or the reciprocal, 

 small-seeded types similar to the small-seeded grandparent and even 

 smaller were obtained in every case, while in some of the crosses 

 involving nearly complete F2 populations (Plates XXV, XXVI), the 

 large-seeded type was also obtained. In all crosses, as expected from 

 studies of size characters in maize, poultry, and other plants and 

 animals, numerous intermediates were present, so that a complete F2 

 population represented a gradating series ranging from those similar 

 to or smaller than the small-seeded parent to those similar to the 

 parent with large seeds. 



Seeds from unbagged F2 small-seeded and large-seeded segregates 

 have given similar F3 progeny, showing the extremes to breed true. 

 Various F2 intermediates have also bred true in F3, while other inter- 

 mediates have given the whole F2 series again. Still others have 

 shown very much less variation. 



Other Characters 



Numerous characters, other than those described in preceding 

 pages, have been studied from the standpoint of heredity, but not in 

 sufficient detail, to admit of interpretation. Crosses between low- 

 growing (dwarfs), early seed-maturing types with determinate growth, 

 and tall, late-maturing types with indeterminate growth gave inter- 

 mediates in Fi, which in F2 gave all three types, though accurate 

 classification so far has been impracticable. Crinkled, much notched 

 leaved types crossed with ordinary leaved types gave either dominance 

 of the ordinary type or intermediates in Fi. Some types have a loose, 

 few-seeded fruiting spike, while others have a dense compact spike 

 with a larger number of pods. Crosses between them give either 

 intermediates or dominance of the loose spike. In Fo, both types 

 reappear, together with many intermediates. 



