R. P. Gregory 129 



lu conclusion, it may be pointed out that here, as elsewhere, families 

 raised from sister plants do not necessarily follow the same system of 

 distribution. Thus the parent of the family 18/10, which apparently 

 conforms to the 3:1:1:3 system, was the sister plant to the parent of 

 the family 17/10, in which the fourth term is smaller than the nudclie 

 ones. 



Note added February 17, 1911. Since the foregoing was written some interesting 

 results have been obtained in connexion with the phenomena of coupling and repulsion. 

 These results are briefly described below. The constitution of a certain type of coloured 

 flower, which was previously uncertain, has also been ascertained. 



Coupling and repulsion. (1) Magenta and short-style. On p. 12-5 a series of experiments 

 is described in which a complete repulsion between the factors for short-style and magenta 

 colour is shown. It will be noticed that in this series of experiments one of the dominant 

 characters was possessed by the one parent race, the other by the other parent. In a new 

 series of experiments a race possessing both dominant characters (i.e. magenta, short- 

 style) was mated with races which bad the recessive characters only. The results show 

 that when the cross is made in this way, partial coupling takes place between the factors 

 for the two dominant characters. 



In the experiments in which the recessive parent was a long-styled red with double 

 flowers, the coupling shown is almost certainly of the form 7:1:1:7; in these experi- 

 ments there is no indication that coupling occurs between either the factor for short-style 

 or that for magenta and any third factor. 



In a second set of experiments, in which the recessive parent was the long-styled 

 "Crimson King," the form of the coupling between magenta and short-style is as yet 

 uncertain, the numbers obtained being almost exactly intermediate between the expectation 

 based on the series 7:1:1:7 and that based on the series 15 : 1 : 1 : 15. In these 

 experiments there is clear evidence that the factor for magenta is coupled, not only with 

 the factor for short-style, but also with the factor for green stigma. The coupling between 

 magenta and green stigma is of a much lower order than that between magenta and short- 

 style. 



(2) Light red stem and green stigma. A new instance of complete repulsion between 

 two factors has been obtained. The factors are (1) the pallifying factor for stem colour 

 (p. 100), and (2) the factor for gi'een stigma. This repulsion was observed in the progeny 

 of a cross between "Crimson King " and "Ivy Leaf." Certain individuals of the F^ from 

 this cross were tested by self-fertilization. Three of these plants, all having light red 

 stems and gi-een stigma, were found to be heterozygous in these characters, giving offspring 

 having either light or dark red stems, and either green or red stigmas, but none of the 

 dark-stemmed offspring had red stigmas. 



Floicer colour. The deeply tinged type of flower shown in Plate XXXI, fig. 32, the consti- 

 tution of which was formerly in doubt, has proved itself to be heterozygous for the factors 

 which inhibit flower-colour. Self-fertilized, it has thrown tinged whites with gi'een stigma, 

 " Duchess " and " BuUer " types with red stigma, coloured with green stigma and coloured 

 with red stigma. The flush shown in the "Duchess "and "Duller" types is of a very 

 deep kind, and the coloured types have flowers of a very deep crimson, at least as deep as 

 that of " Crimson King. " 



