18 On the Colour and Smell of Plants. 



It is hence apparent, that the Rubiacese contain, on an ave- 

 rage, more white flowers than the previously examined families. 

 Of the three principal colours, the Rubiaceae have the greatest 

 tendency to the development of red flowers, and the least to 

 that of blue, a result which seems to be connected with the 

 occurrence of red and reddish-brown colouring matter in their 

 roots and barks, and of vegetable acids in their leaves and 

 fruits ; the last are found in the succulent fruits of the Vaugue- 

 ria cdulis, Vahl ; Morinda citri/blia, L. ; Ixora coccinea, L. ; 

 Ixora alba, L.; Gardenia edulis, Poir.; Genipa Americana^lu.^ 

 Genipa esculenta. Lour. ; and Pavetta indica, L. ; in fresh coffee 

 beans ; in the leaves and flower-stalks of the Nauclea orientalis, 

 Lam., and Uncaria acida, Roxb. ; in the leaves and stems of 

 Galium verum and gracum, L. ; and in the barks of several 

 species of Cinchona. If we now deduce from these and the 

 previously communicated data, a general mean for the distri- 

 bution of colours in flowers, we obtain the following results : 



The 700 more particularly examined Rubiaceae contain 83 

 odoriferous species ; hence, on an average, 11.5 per cent.; a re- 

 sult differing somewhat from the number previously deduced 

 (100 : 9.9). Nearly all have an agreeable smell. 



If we divide the 83 odoriferous species according to the prin- 

 cipal colours, we have the following result : 



If we examine the intermediate colours, orange, violet, and 



