76 Studies of Inheritance in the Japanese Convolvulus 



the two parents and the F^ hybrid are to be represented as follows, 

 respectively : 



parent A = CCrr, 



5 = CCRR, 

 F^ = CCRr. 



From these considerations it will be quite evident that the ratio of 

 plants with coloured and white flowers is 3 : 1. 



I will go now to the consideration of the interrelation existing 

 between the hereditary behaviour of leaf-colour and dark-red flower- 

 colour. Flowers of the latter colour never appear in yellow plants but 

 exclusively in green ones. It was stated before that this constitutes no 

 case of coupling or repulsion (p. 65), and the results of experiments which 

 are now to be described led me to the conclusion that in the presence 

 of a certain factor D, tlte flower is either dark-red or of some other colour 

 according as the green factor G is in either homo- or heterozygous con- 

 dition (or altogether absent). 



There are many instances in which the intensity of flower-colour 

 varies according to the homo- or heterozygous condition of the factor 

 concerned in pigmentation. Thus the flower-colour was found to be 

 lighter in heterozygous than in homozygous individuals, for example in 

 Atropa Belladonna^, Datura Tatula x D. Stramonium'^, Linum usitatis- 

 simum'^ and Antirrhinum majus^. Although our case has not to deal 

 with the intensity of flower-colour, I think that it has to be ranked 

 among the same class of phenomena as those above cited. Similar 

 examples are also found in respect to the pigmentation of other plant 

 organs, as in Corchorus capsularis^, Egyptian cotton^ Indian cotton^, and 

 Phaseolus vulgaris^. Saunders reported an interesting case of the con- 

 nection between the factors for hoariness of leaves and flower-colour in 

 Stocks'^ Colour is due here to the presence of two factors C and R in 

 the zygote. In certain strains of Stocks, the hoariness of the leaves has 

 been found to depend also on the presence of two factoids H and K. 

 Between these two pairs of factors there is a certain relationship, viz. 



^ Bateson and Saunders, Rept Evol. Com. Roy. Soc. 1901, pp. 1 — 160. 



2 L.c. 



^ T. Tammes, Rec. Trav. Bot. Neerl. Vol. viii. 3, 1911, pp. 201—288. 



^ E. S. Finlow and I. H. Burkill, Mem. Depart. Agric. India. Bot. Vol. iv. 4, pp. 73—92. 



5 w. L. Balls, Journ. Agric. Sci. Vol. ii. 1908, pp. 346—379. 



« H. de Vries, Ber. Deut. Bot. Ges. Vol. xviii. 1900, pp. 83—90. 



7 H. M. Leake, Journal of Genetics, Vol. i. 1911, pp. 205—272. 



8 G. H. Shull, Amer. Nat. Vol. xvir. 1908, pp. 433—451. 



^ E. R. Saunders, Proc. Roy. Soc. Vol. lxxxv. B, 1912, pp. 540—545. 



