360 



The Journal of Heredity 



SMOOTH BLACK PLANTS.— Seed- 

 ling families were raised from three F2 

 plants which produced enough ripe seeds. 

 One family was constant black, and two 

 families segregated into. 



Black. 

 53 

 (Calculated 53 



White. 

 18 

 18) 



Hence the progeny of heterozygous 

 smooth black plants segregates into, 



Black. 

 3 



White. 

 1 



The pods of these recessive white 

 plants have not been seen. Most of the 

 F2 smooth black plants yield no crops. 



WORKING HYPOTHESIS. 



If B is a positive genetic difference 

 (or factor) which the Velvet bean lacks, 

 but which is present in the Lyon, Yoko- 

 hama, and China; and C is another 

 genetic factor, present in the Velvet 

 bean, but absent in the other three; and 

 both B and C (either single or double) 

 are needed for the production of typical 

 stinging V^ristles; then in the second 

 generation, 



(1) The stinging plants have both the 

 factors B and C, single or double, 



(2) The downy plants have only the 

 factor B, single or double; 



(3) The long black and "Velvet" 

 plants have only the factor C, 

 single or double; 



(4) The smooth black plants have 

 neither B nor C. 



If D is a genetic factor, present in the 

 Lyon and Yokohama, but absent in the 



Velvet bean, which factor, in the absence 

 of B, causes the formation of black 

 tomentum all over the plant ; if between 

 factors C and D there is a partial re- 

 jDulsion, so that they rarely enter the 

 same gamete; then, 



(1) Plants with neither C nor D will 

 be very rare in F2; 



(2) Plants' with both C and D will be 

 about twice as numerous in F2 as 

 plants with only C; most of the 

 former will have single, and most 

 of the latter double factors; 



(3) Plants with D only will mostly 

 have this factor double, and will 

 be about half as numerous as 

 plants with both C and D. 



We have then for the segregation 

 in F2: 



(1) Nine-sixteenths, stinging plants, 

 all with B and C, about two- 

 thirds with D (mostly single), 

 and about one-third without D; 



(2) Three-sixteenths, downy plants, 

 all with B, and nearly all with D 

 (mostly double) ; 



(3) Three-sixteenths, ])lanls with long 

 tomentum, all with C, about two- 

 thirds (long black) with D 

 (mostly single), and about one- 

 third ("Velvet") without D; 



(4) Nearly one-sixteenth, smooth 

 black plants, without B or C, all 

 with D (mostly double) ; 



(5) A very few, recessive downy 

 plants, without B, C, or D. 



This hyix)thesis needs confinnation, 

 especially by crossing and back-crossing 

 the constant lines in F6. 



Eugenics Research Association 



The Eugenics Research Association, an organization composed largely of field 

 workers on various cacogenic lines, held its second annual meeting at Columbia 

 University on June 19 and 20, with an attendance varying from 50 to 75. A number 

 of good ])apers were read, and much time devoted to a discussion of i)ractical prob- 

 lems, during which considerable dissatisfaction was expressed with the idea that 

 feeblemindedness is a "unit character," Professor R. S. Woodworth of Columbia 

 University declaring that eugenics ccnild not hojjc to gain the supi)()rt of i)sycholog- 

 ists until it had either ])ro\^ed or abandoned this hyj)othesis. Professor J. McKeen 

 Cattell of Columbia University was elected ])resident and William F. Blades of the 

 luigenics Record Office re-elected as secretary-treasurer. Dr. Jean Weidensall of 

 the Laboratory for Social Hygiene, Bedford Hills, N. Y. and Dr. A. J. Rosanoff of 

 Kings Park Hospital, N. Y., were chosen as directors to fill three-year terms. 



