SEED COAT COLOR IN GARDEN BEANS. 79 



The Behavior of Eyedness. 



In many varieties of pigmented beans the pigment is centered around the 

 hilum, producing the eyed bean. The eye may be restricted to a very 

 small area near the hilum, or it may extend over nearly the entire bean, and 

 in some varieties there are found detached circular spots on the dorsal 

 or lateral portion of the bean. In most if not all such cases the pigmented 

 area around the hilum is large. Leopard Wax is a variety of this sort. The 

 pigments and different types of mottling found in totally pigmented beans 

 may occur in any size or type of eye. In most cases the edge of the pig- 

 mented area is not sharply defined, but in others it is clear-cut and definite. 

 No varieties with this sharply defined edge have been used in the crosses 

 here reported, but they have been extracted from certain of the crosses. 



The behavior of crosses of totally pigmented and eyed beans made in 

 the course of this work is shown in Table IX. It closely resembles that 

 of a monohybrid, but the proportions in the r2 generation are somewhat 

 at variance with the expectation. The total number of plants in F2 is 

 1705, and the ratio 3.9:1. Nearly all crosses show an excess of 

 totally pigmented beans. The progeny of heterozygous parent plants in 

 F3 and F4, totaling 2,069, show a ratio of 3.02:1. Why this difference in 

 the behavior in heterozj^gous plants occurs, it is impossible to explain at 

 present. We can only repeat the suggestion made with reference to results 

 shown in previous tables (page 65). All extracted eyed beans have bred 

 true, and in all cases the beans of the Fi generation have been totally 

 pigmented. 



In Table X. are shown the results of crosses of eyed and white beans. 

 In all these crosses totally pigmented beans are produced in Fi. In the 

 F2 generation totally pigmented, eyed and white beans are produced in 

 the proportions shown. It is probable that these plants are of four classes 

 and may yield all three tj^es, totally pigmented and eyed, totally pig- 

 mented and white, or they may be homozygous for total pigmentation. 

 Eyed beans may be pure or may yield eyed and white. 



These results are in harmony with the conclusions of Emerson (5) and 

 Tschermak (22), and indicate that total pigmentation is dependent upon 

 two characters, — P for pigmentation and T, which spreads the pigment 

 over the entire bean, and the absence of which, Pt, causes an eyed bean. 



As has been the experience of previous experimenters we have found 

 no beans with the formula pt. However, we have used only five white 

 seeded sorts, and only three pi these at all extensively. The white beans 

 extracted from an eyed parent in crosses 249, 268 and 327 should be of 

 this constitution, and should yield no totally pigmented beans on crossing 

 with an eyed form. Unfortunately, none of these few white seeded plants 

 were self-fertiUzed or retained for seed, making it impossible to test this 

 theory. » 



The fact that eye sizes differ has been mentioned. While too few 

 accurate data have been collected in the course of these experiments to 

 make any definite report, it is evident that these eye sizes are inherited 



