174 ANTHOCYANINS AND GENETICS 



points out that there are however other strains of mottled beans which 

 do breed true. 



Emerson (528) publishes a long paper on pigmentation in bean seeds. 

 He gives first a list of the crosses made by Tschermak, Shull and himself. 

 He points out, as Shull has done, that there are two kinds of mottled 

 beans, viz., strains which breed true, and heterozygous forms not 

 breeding true. Emerson then suggests a scheme to explain the existence 

 of two sorts of mottling, namely by postulating two factors for mottling : 

 M the sort of mottling which breeds true, and X, the sort which is visible 

 only in the heterozygous condition. The results he obtained experi- 

 mentally can be explained on the basis of this scheme. In .a later 

 paper (529) Emerson gives further results of the inheritance of total 

 and eyed (round hilum) pigmentation, but since the kind of pigment 

 is not described, it is not clear how far it concerns anthocyanin. 

 Emerson also mentions another hypothesis suggested to him by Spillman 

 to explain the two kinds of mottling mentioned above. Spillman sup- 

 poses that the mottled races which breed true have in them two corre- 

 lated factors, and that there are three types of non-mottled beans 

 resulting from the 16ss of one, or the other, or of both of the correlated 

 factors. On Spillman's plan, just as on Emerson's two factor hypothesis, 

 a definite formula can be assigned to all the races used in crossing, and 

 in this way all the results, with one or two exceptions, can be accounted 

 for. Emerson himself inclines to the coupled-factor, rather than the 

 independent-factor, hypothesis. 



Pliyteuma. Inheritance of anthocyauin in the cross Ph. Halleri 

 x Ph. spicatum. Correns (486). 



Pisum sativum. Here again as regards pigmentation, the colour 

 of the testa has received a great deal of attention. Bateson & Killby 

 (487) noted that greys and browns in the seed-coat are associated with 

 coloured flowers, and crossed with whites they occasionally give 'rever- 

 sionary' Fj with purple (anthocyanin) spots, though spots were absent 

 from the parents. 



Lock (512, 518) sums up many of the results on pea colour. He 

 states that the albino variety has no anthocyanin. The presence of 

 a factor C produces grey (chromogen) in the testa, and red anthocyanin 

 in the leaf axils and flowers. The presence of S produces spotting of 

 a reddish shade on the testa. The presence of P modifies red anthocyanin 

 of the axils, flowers and spots on the testa to purple. 



Polemonium. Inheritance of blue anthocyanin in F t from cross of 

 P. caeruleum by P. flavum. Correns (486). 



