STUDIES ON THE GENETICS OF FLOWER-COLOUUS, ETC. 1(15 



From Tiible IV as well (is wli.it 1 Imvo jus*: stjited we will soo that we 

 lijive here appiireutly to deal with a typicid case uf dihybrid segi'Ogation. 



lu tlie various ciises studied till now by several authors it was foiuid 

 that for the productiou of I>hiish-red c-olonr (niagouta, purple, etc.) the factor 

 for produciug the red authocyauin and tha^ for changing tlie latter into 

 bluish-retl one participate ; thus, for instance, in flowcre of Laihyrus odoratus 

 (JJ iUid B, Bateson)', and of Antirrhinum majus {F, It, D, Baur;' R or L, 

 T and H, Miss Wheld^vle),' in the aleurone of ISIjiize {R and P, East and 

 Hayes ;^ R and Vi', Emeuson),'' etc. The question naturally arises whether 

 tlie magenta colour of flowei-s of Porkdaca is not also due to the combine;! 

 action of such factors. The results of our present cros^ do furnish, as will 1« 

 seen fi-oia \\hat was stated above, no positive evidence towards such a 

 0jnclusiou, V)nt some other breeding experiments, espscially the CVoss ^'III 

 (p. 112), prove beyond all doubts that tlia magenta colour in our case is 

 due, quite similarly as in all cases above cited, to th3 action of the two 

 factors which I call R (reddening) and R (blueing) respectively. We liave 

 therefore iu the hybrid wliite-I X magenta or its reciprocal a ti'ihybrid instead 

 of a dihylirid, inasmuch as it may be expressed by the genetical formula 

 CcRt'Rb, as above given. If the three factors C, R, R contained iu this 

 hybrid will make free assortment, we should have eighj kinds of male and 

 female gametes, i.e. CRB, cRB, CvB, crB, CRb, cRb, Crh, crh, and 

 consequently the ratio of 27 magentas : 9 reds : 12 oranges : IG whites iu FJ' The 

 reason why not^\ ithstauding this we have in our case the ratio of 9 magentas : 

 3 oranges : 4 whites in F, will be seen, when we think that of the thi'ee 

 factoi-s C, R, B contained in magenta the two latter are iu the state of 

 complete " coupling " or " linkage " (to use the word more fi-equently adopted 

 recently), and act just like one single factor, so that we have here simply 

 four kinds of male and female gametes, i.e. CRB, cRB, Crh, ci'b. If R 



• JIenue^'s Prinriples of Ikr'ditij. p. 'Jl. 



- Zeitsclt. f. irul. Abstamm. u. Vererhnngs'ehre, Bd. 3, 1910, pp. 41-43. 



» Ibid., p. 326 ; nlso Joum. of Genetics, Vol. 4, 1915, p. 110. 



4 Conn. A'jric. Exp. Stat.. Bull. No. 167, 1911. 



^ Cornell Cniv. .l|;ric. Exp. Stat., Memoirs 16, 1918. 



" This is somewhat similar to the /«'j-genenilion of the classical example o£ Sweet Pea (s. 

 Bateson-, 1. c, p. 91), though we have in the latter 28 whites instead of 12 oranges smX 16 



whites, since the factor C does not produce any colour in Sweet Pea. 



