218 Sttulies in IiuViun Cotton 



The red type 3 possesses the two dominant, and the white type 9 

 the two recessive, factors. Denoting these two pairs by the letters Rr 

 and Yy, the two parental types will bear the constitution KFand ry, 

 and the six groups which have been recognised the constitution given 

 below with the numerical proportion between the individuals which is 

 assigned to eacli group: 



(1) ««"■ Mo^ 



RRYy -2 P I 



(2) KrYY 2j [ * 



RrYy 4^ J 



(3) HRyy 1 \g 



W liniV -i J 



'■'•ly 2S ) 



(6) rnj,j 1 1 



The plants of the first group can be separated into two subsidiary 

 groups, the members forming the one being pure with regard to both 

 characters, while those forming the other will be pure with regard to 

 the red, and impure with regard to the yellow, character. Groups (2) 

 and (5) can be similarly divided and in all cases this division will be 

 recognisable in the offspring. How far these assumptions are borne 

 out in experiment will be seen from Table VII where the results of 

 this cross are set out in detail. In all cases the expected groups have 

 been formed and the actual numbers are in close accordance with those 

 expected on the above scheme. 



The facts concerning the petal colour and the red anthocyanic 

 colouring matter of the sap are, tlierefore, fully explained on the 

 assumption that two pairs of allelomorphic characters enter into con- 

 sideration, these two pairs being composed of the two fiictors producing 

 the red colour and the yellow colour respectively, the presence of the 

 colour producing factor being in both cases the dominant, and its 

 absence, the recessive, condition. 



Starting with the red and the white flowered type, it has been 

 found possible not only to produce, but to produce in a state of purity, 

 two other types, one having a yellotu (PI. XXXV), and the other a red 

 on white (PL XXXV), flower. Apart from complications introduced by 

 the consideration that one of the parents is a monopodial, late flowering 

 type, which may be put aside for the moment, the yellow flowered 

 form is recognisable as type S, and similarly the red on white flowered 



