xi THE SPECIAL COLOURS OF PLANTS 319 



Crista -galli) ; while in drier meadows we have cowslips, 

 ox-eye daisies, and buttercups, all very distinct both in form 

 and colour. So in cornfields we have the scarlet poppies, the 

 purple corn-cockle, the yellow corn -mary gold, and the blue 

 cornflower; while on our moors the purple heath and the 

 dwarf gorse make a gorgeous contrast. Thus the difference 

 of colour which enables the insect to visit with rapidity and 

 unerring aim a number of flowers of the same kind in suc- 

 cession, serves to adorn our meadows, banks, woods, and 

 heaths with a charming variety of floral colour and form at 

 each season of the year. 1 



Fertilisation of Flowers hj Birds. 



In the temperate regions of the Northern Hemisphere, 

 insects are the chief agents in cross -fertilisation when this is 

 not effected by the wind ; but in warmer regions, and in the 

 Southern hemisphere, birds are found to take a considerable 

 part in the operation, and have in many cases led to modifi- 

 cations in the form and colour of flowers. Each part of the 

 globe has special groups of birds which are flower-haunters. 

 America has the humming-birds (Trochilidae), and the smaller 

 group of the sugar-birds (Caerebidse). In the Eastern tropics 

 the sun-birds (Nectarineidae) take the place of the humming- 

 birds, and another small group, the flower-peckers (Dicseidse), 

 assist them. In the Australian region there are also two 

 flower-feeding groups, the Meliphagidse, or honey -suckers, 

 and the brush -tongued lories (Trichoglossiclse). Eecent re- 

 searches by American naturalists have shown that many 

 flowers are fertilised by humming-birds, such as passion- 

 flowers, trumpet -flowers, fuchsias, and lobelias ; while some, 

 as the Salvia splendens of Mexico, are specially adapted to 

 their visits. "We may thus perhaps explain the number of 

 very large tubular flowers in the tropics, such as the huge 

 brugmansias and bignonias ; while in the Andes and in 



1 This peculiarity of local distribution of colour iu flowers may be com- 

 pared, as regards its purpose, with the recognition colours of animals. Just 

 as these latter colours enable the sexes to recognise each other, and thus avoid 

 sterile unions of distinct species, so the distinctive form and colour of each 

 species of flower, as compared with those that usually grow around it, enables 

 tbe fertilising insects to avoid carrying the pollen of one flower to the stigma 

 of a distinct species. 



