22 On the Colour and Smell of Plants. 



We also observe in this family an increase of odoriferous spe- 

 cies as the amount of colouring matter diminishes, a remark we 

 have several times had occasion to make in the preceding investi- 

 gations. In the last of the quoted essays notice is particularly 

 taken of the relations of colour and smell in the families which are 

 most abundant in our climates. By including these families in a 

 general view, and arranging them according to the relations of 

 their odoriferous species, these being reduced to a per-centage, we 

 obtain a nearer approximation to the more general distinctions in 

 regard to colour and smell. There flower in the mean of 100 

 species, 



Of the families here enumerated, the Nymphaeaceae and Rosa- 

 cese contain, in proportion, the largest number of white flowering 

 species, and the Papaveraceae and Campanulaceae the fewest ; 

 the two first include at the same time the largest number of odo- 

 riferous species, and the two last by much the smallest, and of 

 these several have disagreeable odours. 



The Primulaceae and Convolvulaceae are richest in red flow- 

 ering species. Jn the first many have yellow flowers, and in the 

 last many have blue. The first are richer than the last in plants 

 having an agreeable smell. 



The Campanulaceae are richest in blue flowers ; then follow 

 the Asperifoliae, which have at the same time a much greater 

 tendency to white and yellow flowers ; the last also possess a 

 much larger number of plants having an agreeable odour. 



Lastly, the Ranunculaceae, in the genus Ranunculus, have a 

 great many yellow flowering species ; but most of the other ge- 

 nera flower in the tints of the bluish-red colour series ; they con- 

 tain few odoriferous species, and of these many in proportion 

 have disagreeable odours. 



