Cbap. X. MEANS OF CROSS-FERTILISATION. 375 



days or weeks and do not attract any insects ; and it is 

 probable that they are neglected from not having as 

 yet secreted any nectar or become odoriferous. Nature 

 may be said occasionally to try on a large scale the 

 same experiment as that by M. Plateau. Not a few 

 flowers are both conspicuous and odoriferous. Of all 

 colours, white is the prevailing one; and of white 

 flowers a considerably larger proportion smell sweetly 

 than of any other colour, namely, 14*6 per cent. ; of 

 red, only 8 2 per cent, are odoriferous.* The fact of 

 a larger proportion of white flowers smelling sweetly 

 may depend in part on those which are fertilised by 

 moths requiring the double aid of conspicuousness in 

 the dusk and of odour. Most flowers which are fer- 

 tilised by crepuscular or nocturnal insects emit their 

 odour chiefly or exclusively in the evening, and they 

 are thus less likely to be visited and have their nectar 

 stolen by ill-adapted diurnal insects. Some flowers, 

 however, which are highly odoriferous depend solely 

 on this quality for their fertilisation, such as the night- 

 flowering stock (Hesperis) and some species of Daphne ; 

 and these present the rare case of flowers which are 

 fertilised by insects being obscurely coloured. 



The storage of a supply of nectar in a protected place 

 is manifestly connected with the visits of insects. So 

 is the position which the stamens and pistils occupy, 

 either permanently or at the proper period through 

 their own movements ; for when mature they invariably 

 stand in the pathway leading to the nectary. The 

 shape of the nectary and of the adjoining parts are 

 likewise related to the particular kinds of insects which 



* The colours and odours of I have not seen their original 



the flowers of 4200 species have works, but a very full abstract 



been tabulated by Landgrabe, is given in Loudon's ' Gardeners' 



and by Schiibler and Kohler. Mag.' vol. xiii. 1837, p. 307. 



