150 BREEDING CROP PLANTS 



The Lyon bean has a whitish stiff pubescence on its young shoots, 

 leaf and calyx. The hairs on the pods form a fine down and 

 average 0.5 mm. in length. The FI was covered with irritating 

 hairs. The hairs on the pods were about 1.5 mm. long. These 

 contain a gummy substance in the hollow points and readily 

 pierce the human skin, causing an irritation lasting several 

 minutes. In F 2 about nine-sixteenths of the plants bore stinging 

 pods (long stiff hairs which pierce the skin). Some were more 

 developed than in FI. Two factors are necessary for the produc- 

 tion of stinging pods. One of these factors, B, is contained by 

 the Lyon bean while C is contained by the Velvet bean. Color 

 of pubescence showed segregation in F 2 , giving 13 whitish to 

 3 black pubescent plants. The dehiscence of pods behaved as 

 a dominant. Most of the pods on the FI plants burst open when 

 mature. In the F 2 generation segregation occurred. Long 

 pods crossed with short pods gave approximately a 3:1 ratio in 

 the second generation although minor factors for pod length were 

 discovered. In the inheritance of seed color it has been suggested 

 that three factors are concerned, each of which produces some 

 mottling even when heterozygous and in the absence of the two 

 other factors. Purple color appears in the Florida velvet bean 

 on the under surface of the first pair of simple leaves, on the 

 stems as a mark on the leaf axil, on the wings and standard and on 

 the stems and petioles on the side exposed to the sun; while the 

 Lyon lacks the purple color. Purple color proved dominant in 

 FI and a 3:1 ratio was obtained in F 2 , only a single factor being 

 involved. The characters, time of flowering, size of flower 

 clusters, and size of plant gave unmistakable evidence of segre- 

 gation in the second generation. Each of the crosses Florida 

 x Lyon, Lyon x Florida, and Florida x Yokohama produced about 

 50 per cent, pollen sterility in the FI generation. Aborted ovules 

 were found on plants showing pollen sterility. Belling satis- 

 factorily explained the results by postulating two factors, K pres- 

 ent in Florida, and L present in Lyon and Yokohama. The 

 presence of either K or L, but not both, gave rise to normal 

 pollen and ovules. Combinations of KL or kl in the gametes 

 resulted in pollen or ovule sterility. 



Mutations. Coe (1918) has attributed the origin of early 

 maturing velvet beans to mutations. C. Chapman and R. W. 

 Miller, both of Georgia, and H. L. Blount of Alabama, separately 

 discovered early maturing mutants growing in fields planted to 



