332 



CHAPTERS ON EVOLUTION. 



rule, associated in flowers with a faint development, or even a want 

 of scent. Insects being attracted by one quality or the other, the 

 presence of scent would be useless where colour is well developed. 

 If we compare such flowers as pelargoniums, convolvulus, pansy, 

 fritillary, c., which are conspicuous and bright tinted, but scentless, 



FIG. 233. SECTION OF FUCHSIA. 



FIG. 234. FUCHSIA. 



with the primrose, lily of the valley, rose, and hyacinth, which are 

 not so conspicuous, but emit powerful odours, we can realise the 

 principle of nature's economy in avoiding over-lavish provisions for 

 insect-attraction. The correlation between flower and insect is 

 even more strongly marked, however, when we discover that flowers 

 which are fertilised by night-flying moths are usually of white 

 colour, so as to appear conspicuous at night, and may further emit 

 their odour only or chiefly at night. Such flowers as Daphne and 

 Hesperis obscurely coloured, as it happens attract insects solely 

 by their powerful odour. Nageli's experiment of scenting artificial 

 flowers with essential oils was followed by the attraction of insects 

 "in an unmistakable manner." 



The description of a few of the most typical cases in which 

 cross-fertilisation is found may fitly conclude the more exact 

 consideration of the present topic, and preface the abstract philo- 



