1887-88.] Colouring Matters of Leaves and Flowers. 303 



tion that colour is not a sexual allurement " (we might say, 

 is not to be regarded only as a sexual allurement), " or we 

 should find it most developed, not in conjunction with, but in 

 the absence of, the attractive odour." 



Other instances of the correlation of colour to size or 

 vitality among animals as among plants, will suggest them- 

 selves to the biologist ; for instance, in the male " stickle- 

 back" we recognise true and physiological significance in its 

 indication of an exuberant vitality; for it has, no doubt, some 

 purpose in indicating to the female the exceptional power of 

 a would-be mate, just as in the spring " the freer crimson 

 on the robin's breast " may be supposed to do likewise ; but 

 it was not because the female fish or bird liked colour per se 

 that this was developed. 



It is needless to refer in any detail to the evidence, which 

 is overwhelming, in favour of a regular series of colours 

 indicating progressive development, in such elaboration of 

 further products. From the reactions of colouring matters, 

 from the changes in the life-history of the individual and 

 of the race, it is clear, as pointed out by Mr Grant Allen, 

 that such a series from yellow to white, passing to red and 

 blue, is a natural one. We do not need, however, to recog- 

 nise that all the coloured whorls of flowers came from yellow 

 stamens, for we have seen that green being the colour of 

 vegetation, with its essential function of carbon-assimilation, 

 yellow is but a stage to this, which may be given to any 

 organ for a longer or shorter time as vegetation is checked ; 

 whilst white and red are also produced by its further or con- 

 tinuous checking ; no considerations of morphological evolu- 

 tion affect the question. 



We have thus a physiological meaning to give not alone 

 for green, and for " colour " as opposed to green, but each 

 colour, rightly considered, may have for each plant a special 

 significance. 



Darwin showed that the commonest variation of the 

 Japanese Chrysanthemum was the production of yellow ; in 

 which doubtless the garden varieties reverted to a simpler 

 colour more nearly like that of the chromoplast of their 

 ancestors, than that resulting from the high art of the 

 Japanese cultivator. Similarly, it would not be difficult to 

 explain, in terms of increased or diminished possibilities 



