72 ANIMAL LIFE 



able service of cross-fertilisation to the plants they 

 visit. In the act of dipping the tongue into the 

 corolla to tap the nectaries the insect dusts its head and 

 legs with mealy pollen. Thus powdered, it flies to 

 the next flower or another plant of the same kind, and 

 when unfurling its proboscis strikes gently against the 

 pillared stigma that stands central in the corolla and 

 cross-fertilises it. 



The advantages of cross-breeding over inbreeding 

 are many and great. In vigour, colour, abundance of 

 fruit, crossbred plants are superior to inbred ones. 

 But since plants are fixed organisms, the pollen has 

 to be borne from flower to flower, or from a male tree 

 to a female, by one of the three moving agencies, 

 water, air, or animals. Flowers are in the main 

 devices to attract the notice of animals and to 

 ensure pollination. Brilliancy of colour, definiteness of 

 pattern, attractiveness of odour, serve to draw the 

 curiosity of animals. The opening of strong-smelling 

 plants by night entices nocturnal creatures to visit 

 them. Of the numerous applicants drawn by this 

 bounty not all are helpful. Sparrows confer no benefit 

 on crocuses by their ruthless destruction of early 

 blooms. Slugs are the gardener's greatest foe. But 

 the great majority of flying insects are drawn, not to 

 an indiscriminate destruction of the flower, but to the 

 nectaries, or honey-sacs, which secrete the odour from 

 within it. 



The interaction between flowers and the insects 

 that visit them is one of the most interesting chapters 



