90 



MASS. EXPERIMENT STATION BULLETIN 185. 



represented by the formula PTYzmG, and that of the black wax varieties 

 by PTyZMG, either or both having possible additional hypostatic de- 

 terminers, we have in effect a simple monohybrid based on the presence 

 or absence of the modifier M with its accompanying mottling factor Z. 

 This gives a proportion 3M:lm. Two of the plants carrying the modifier 

 are heterozygous and mottled, while one is homozygous and is solid 

 black. Inasmuch as Y and Z are confined to different gametes, according 

 to Emerson's hypothesis, no zygote PTyzm is possible. Thus we have the 

 theoretical proportion 1 black, 2 mottled, 1 buff, which is borne out by 

 the facts presented in the table. 



Table XVI. — Crosses of Blue Pod Butter with Black Wax Varieties. 



The variety Bountiful has seeds that bear some resemblance to those 

 of Blue Pod Butter. They have been recorded bj^ the same symbol, B. 

 The flowers are pink instead of crimson, and the plants do not show the 

 marked purplish tinge. It has been used in crossing to a limited extent 

 only. In Table XVII. are tabulated the results of crosses with two black 

 wax varieties. From the results of other crosses we have assigned to the 

 black wax varieties the black, brown and, in some cases at least, the 

 yellow determiner. In these crosses with Bountiful all these colors appear 

 as well as the H color, the behavior of which we do not clearly under- 

 stand. This indicates that Bountiful does not possess any of these de- 

 terminers. Buff-colored beans appear only in small numbers, indicating 

 that it does not lack the modifier M. If we assign to Bountiful the formula 

 PTyZMgfc, and to the black wax varieties the formula PTyZMGFC, 

 the results of crossing would be in harmony with the limited data shown 

 in Table XVII. 



