190 ANTHOCYANINS AND GENETICS 



flower-colour varies to pale yellow (see p. 150) the orange-red blotch 

 then appears as carmine. The red anthocyanin may give rise to a purple 

 variation and there are correspondingly coloured blotches, maroon on 

 a deep yellow and purple on a pale yellow ground. 



Reviewing the cases of pattern set out above we are able to distinguish 

 several different types. One type, for instance, includes all those spots, 

 lines and streaks which form a normal part of flower-coloration and 

 which, in the opinion of biologists, have a significance as signals or guides 

 to insect visitors. This group would include the markings in Cypri- 

 pedium, Digitalis, Erodium, Mimulus, Papaver, Primula and Tropaeolum. 

 As far as can be judged from the evidence at hand, some of these patterns 

 (Papaver, Tropaeolum) are inherited independently of the ground colour 

 of the flower ; the factors for others are intimately associated in various 

 ways with the ground-colour factors (Digitalis, Primula). A second 

 type of pattern is that which is not a feature of the normal flower- 

 coloration, but is only revealed in varieties from which some of the 

 colour factors are absent, for example the ' delila' variety of Antirrhinum 

 and the 'Duchess' and 'Sirdar' varieties of Primula. A third type of 

 pattern, for instance the spots on Arum leaves, the leaf-spot of Gossypium 

 and the mottling of seeds of certain strains of Pisum and Phaseolus, 

 forms a normal attribute of the plant to which we. can assign no special 

 significance. 



As regards the nature of the factor which produces mosaics or 

 mottling in seed-coats we cannot at present offer any interpretation. 

 It apparently limits the distribution of colour to certain areas ; whether 

 this is due to inhibition of pigment, or whether it is due to the fact 

 that the pigment formed in the plant is less, and hence insufficient to 

 give self-colour, cannot be decided. But it is evident that the mottling 

 factor is one apart from colour and can be carried by albinos. Bateson 

 (524) draws an interesting comparison between colour-pattern and 

 dilution. In both cases, he points out, less pigment is present in the 

 zygote, but in one case the area is diminished though the intensity 

 remains the same, in the other the intensity is diminished, but the 

 area of coloration is constant. 



STRIPED VARIETIES AND BUD- VARIATION. 



A common form of variation in many flowers is striping, i.e. the 

 arrangement of colour in bands or stripes; these markings may vary 

 in thickness from the narrowest hair-like streaks to broad bands, or 

 elongated patches, which may then occupy almost the whole of the 



