R. P. Grbgory 116 



heterozygous for the factor determining the purplish-red stem and deep 

 colour of " Crimson King," which is present both in that race and in 

 *' Snowdrift." In addition therefore to the types found in the "Crimson 

 King" F^ there appear extracted "Orange Kings," and a new class 

 consisting of plants with pink or pale-pink flowers and stem-colours 

 ranging from red collar to reddish stem. These plants are no doubt 

 derivatives of "Orange King," whose appearance they rather recall; 

 but further experiment is required upon this point, as well as upon the 

 further point as to whether the " Sirdar " character is recognizable as 

 such, if, and when, it occurs in the " Orange King " series of pigments. 

 The numbers obtained in two F, families were : 



Pink, PiJepink, 



red collar to faint tin^e or .Mliite, 



Full colour " Sirdar " '' Orange King " reddish stem no colour m stem green stem 



111 33 5 29 52 12 



178 64 



The numbers given in the last three classes can only be regarded 

 as approximately representing their relative sizes, since one can hardly 

 avoid some experimental error in a separation guided by external 

 appearance only. It will be seen that, if the pink class prove to be 

 derivatives of " Orange King," the numbers obtained agree with the ex- 

 pectation based on the hypothesis suggested by the result of the cross 

 (" Crimson King" x " Orange King"), namely, that the subtraction of a 

 single factor will suffice to explain the behaviour of the "Orange King" 

 type of pigment. 



The existence of some form of partial gametic coupling between the 

 magenta and green stigma is clearly indicated (see p. 127). 



(3) Inhibition of Colour in the Flower. 



All the red-stemmed whites with which I have worked have been 

 found to possess the factors which inhibit the development of colour 

 in the flower; when crossed with the albino "Snowdrift," they have 

 given colours in F^. Since fully coloured flowers only occur in con- 

 junction with fully coloured stems, the stem-colour of the dominant 

 white is a guide to the flower-colours which may appear in the F^; 

 those with full red stems will give full colours, while those with no 

 more than a tinge of colour in the stem can only give pale-pinks. 

 The precise ratio in which the coloured forms appear in Fj is still in 

 doubt. In the F^'s consisting of whites and pale-pinks only the former 

 are in excess of the expected ratio of 13 : 3. Owing to the difficulty 

 of distinguishing these faint colours, no great weight could be attached 



