viii Preface. 



Their flowers have inconspicuous petals, or none ; ex- 

 hale no sweet odour ; secrete no sweet nectar. They 

 have no object in attracting insects, and consequently 

 appeal to none of their senses. 



It is quite otherwise when the agency of pol- 

 lination is animate. The animate agent is in some 

 comparatively few instances a bird, but as a gene- 

 ral rule is an insect. These must be allured to the 

 flower ; and this accordingly appeals to their sight 

 or smell by brilliant colours and by attractive scents. 

 These colours and these scents draw the insect to 

 the flower from a distance ; but by themselves they 

 would be but empty gratifications, unprofitable to 

 insect and to flower alike. Something more sub- 

 stantial must be offered ; something that will prevent 

 the insect from merely loitering about the flower in 

 idle satisfaction, and that will induce it to probe the 

 recesses of the blossoms, and in so doing to transfer 

 the pollen of one flower to the stigma of another. 

 This further allurement is addressed to the palate ; 

 and though in some cases it is nothing more than the 

 pollen itself, in most it is supplied by the secretion 

 of a sweet fluid, the so-called nectar. 



Now Nature, who at first sight often appears a 

 prodigal, is always found on closer examination to be 

 the most rigid of economists. If no insects are to be 

 allured, she gives, as we have seen, no nectar ; she cuts 

 off the bright petals, and suppresses the attractive 



