8 Bulletin 392 



the parent plant by a dash. The number of dashes in the pedigree num- 

 ber gave, therefore, a clue to the number of generations that the ])edigree 

 had been selt-fertiHzed. Thus, the first plant in a lot of seed was num- 

 bered 15-1, the second 15-2, and so on. When a plant was selfed, its 

 progeny were numbered 1 5-2-1, 15-2-2, and so on. The Fi plants from 

 a cross would be numbered loo-i, 100-2, and so on, or 230-1, 230-2, and 

 so on. 



It may be assumed from the behavior of such pedigrees as those shown 

 in table i that a pure recessive plant when self-fertilized will produce 

 only tan -coated seeds thruout any subsequent number of generations in 

 which the progeny also are self-fertilized. No black-coated seeds were 

 ever produced in any of these pedigrees. 



If black -seeded plants are homozygous, then, when they are self- 

 fertilized, succeeding generations will produce indefinitely black-coated 

 seeds, as is shown in four pedigrees in which the seed coats of the first 

 and second parental and the first filial generations, as well as the plants 

 under consideration, were all black. Here is evidence that the character 

 bred true thru four generations. 



Black -coated heterozygous seeds, however, will give rise to plants the 

 integuments of whose ovules will all be black but whose eggs contain 

 either the dominant or the recessive gene. When self -fertilized, these 

 plants will produce seeds that are either duplex or simplex dominants 

 or pure recessives. 



This hypothesis is supported by the data of pedigrees 100 and 200. 

 In both cases the seed parent of the cross came from recessive stock and 

 the poUen parent from black-coated stock. In both cases all the Fi plants 

 bore black-coated seeds. In pedigree 100 the F2 progeny from one of 

 these black -seeded plants when selfed consisted of 10 blacks and i tan. 

 In pedigree 200 the F2 progeny from one plant consisted of: i tan which 

 when selfed gave rise to 2 5 tans — pure extracted recessives ; i black 

 which gave rise to 4 blacks; and i black which gave rise to 17 blacks and 

 6 tans. In cross 102 the seed parent w^as a recessive and the pollen parent 

 was black -coated, but the latter was evidently simplex for the dominant 

 character because the Fi plants were both black-seeded and tan-seeded, 

 there being 2 blacks and i tan. 



THE GENETICS OF THE FEATHERED COROLLA 



The character here termed feathered is a sort of ragged condition that 

 occurs on the outside of the corolla. Narrow strips and filaments arise 

 about the base of the corolla tube and on its outer surface, fringing it 

 about and giving it a bizarre feathered appearance. 



The origin of this character in the writer's cultures was a single plant 

 out of ten that came from commercial seeds in a ])acket marked Double 





