38 



Colours of Plants 



[CH. 



Plants. 



For the convenience of readers acquainted with the phenomena in 

 outline and desirous of pursuing the subject further the following brief 

 annotations are placed here. Until the chemistry of pigmentation is 

 better understood, a comparison between the behaviour and properties of 

 the several types cannot be instituted with much confidence. 



Antirrhinum. Wheldale (303) has shown that the lowest or hypostatic 

 factor dominant' to albino gives yellow in the " lips " of the flower ; the 

 addition of various other factors produces anthocyan reds which superposed 

 on the yellow give deep crimson red colour. A second series of reds, more 

 purplish or magenta in tint (colour of wild A. majus), results from addition 

 of a factor which in absence of anthocyans gives an ivory colour. This 

 ivory is epistatic to yellow. It is remarkable that the lowest anthocyan 

 factor gives red in the tube with a tinge in the lips, while the addition of 

 the next above it gives the self-coloured flower. 



There is also a white-tuhed. type of each colour-combination (''Delila" 

 of de Vries, 298). 



All the factors except that for yellow and ivory can be carried by the 

 albino. Among the reds several heterozygous combinations can be recog- 

 nized. The heredity of striping is still under investigation. 



Atropa Belladonna. The normal dark-fruited type is dominant to 

 yellow-fruited (de Vries, 290; Saunders, 19). 



