DIFFERENCE IN COLOUR OF FLOWERS AND FOLIAGE. 125 



duces variation, and this probably often means with such 

 plants an increase in brilliancy of colour in the flowers, 

 which would thus seem to be at least correlated with the 

 tendency to infertility above-noted. 



The same suggestions as to infertility may, I think, be 

 applied to wild flowers gi'owing on different soils and under 

 different conditions; but here the tendency to decrease 

 infertility may perhaps be in some measure counteracted by 

 the intercrossing of different species by the visits of insects. 



Coming now to foliage, I think that we shall find the 

 conditions above-named as probably affecting the colour 

 of flowers have here also had a proportionate effect, the 

 foliage of tropical climates being generally of a deeper hue 

 than that of temperate regions. Indeed, the farther we 

 recede from both tropics, north and south, the more as a 

 general rule do we find this to be the case, the more does 

 the lighter hue predominate. 



The causes which tend to produce this difference of hue 

 in the foliage are then, I believe, much the same as in the 

 case of flowers. The comparative absence of sunlight, a 

 warm, damp atmosphere, and a comparatively rich soil, tend 

 to produce a deeper hue in both foliage and flowers, as an 

 abundance of sunlight, a cool, dry atmosphere, and a com- 

 paratively poor soil are more favourable to a brighter 

 colour. 



In conclusion, taking it for granted that we have good 

 reason for believing that in tropical regions a brilliant 

 colour in flowers and a light hue in foliage is the exception, 

 and the reverse the rule, while in more temperate regions a 

 more brilliant hue in flowers and a lighter one in foliage 

 is the rule, and the reverse the exception, I trust that I 

 have been able to throw a little light upon the possible 

 causes of these phenomena. 



