60 I. NAGAI : 



Furthsr we admit that the geue R is present üi the faiut yellow awn plant, 

 and by the completion of the system provided by the genes CB (COR), the 

 chromogenic substance is converted to red authocyanin, but by cR (coR) and 

 cor {cor) the system is incomplete. The parental faint j-ellow plant may there- 

 fore be designated by cR (coR) and the brown plant by Cr ( COr). The retl 

 awn F^ plant is Cc Rr (COcoRr) and by selfing, the following zygotic series 

 would arise in F, by the ratio 9:3:3:1, viz., CR {COR), Cr (COr), cR 

 (coR ), and cor (cor ), and in which the last four would be faint yellows giving 

 rise io 9 reds, 8 brawns and 4 fain^ yellows. The assump'iou covers the 

 numerical ratio observed in the F^ and F^ generations. 



Let us suppose in another way that the brown awn may have the genetic 

 composition COr and the faint yellow cOR, in which is the gene common 

 to both of the parental plants. It is necessary to suppose that no red au- 

 thocyanin should be formed liy eOR in which the chromogenic substance 

 produced is onl}' in such a small amount that no anthocyaniu is formed fi'om 

 it even in the presence of OR. If however, the reduction processes set work- 

 ing by the gene complex here concerned are just as powerful as we provide 

 in vitro by means of hych'ochloric acid and magnesium powder, even a trace 

 of the chi-omogenic substance should be converted to the wloiu-ed anthocyaniu, 

 for, we can readily detect even a fa-ace of the clu-omogenic substance (1 : 20,000) 

 by a distinct ])ink colour by reduction. 



In the case of the cross " Hanbun-nento " x " Genroku-mochi ", in which 

 the purple and red awn are concerned, the basal system of anthocyaniu 

 formation CR is complete in both of the pai-ental plants. If we let the gene 

 R' convert the red anthocyaniu to pm-^jle, the purple awn may be designated 

 by CRR' and the red by CRr'. The designation CRR' may be substituted 

 by a single letter, say P, and CRr' b}- j). Since we observe the stages of the 

 change, chromogen — » red pigment — * purple pigment in the plant, CRR 

 seems to represent the actual phenomena occurring in the sporophyte. 



In a uuuiljor of cases reported, the puiple colour is dominant o^or the 

 red.' In AniirrJihiura ]Miss. Whedale (1914) '.found that orange authocj-auin 



1. See summary in Uatk^ov, \V., Mexdel's Principles of Horcility. Third edition. l!li;i. 

 Whbldale, JI., Anthücynn risnients of Plants IDlfi. 



2. Whei.dale, .M., Oar Present Knowledge of the Chemistry of the ilendelian Factors for 



Flower Colour. .lour. Genet, -i : S, IDl-i. 



