XI THE SPECIAL COLOURS OF PLAXTS 319 



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

 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 o'orse make a o-oro-eous contrast. Thus the diff'erence 

 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 oui^ meadows, banks, woods, and 

 heaths with a charming variety of floral colour and form at 

 each season of the year.^ 



Ferfilimtion of Flotvers by Birds. 



In the temperate regions of the Northern Hemisphere, 

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

 not efl'ected 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 sj^ecial groups of birds which are flower-haunters. 

 America has the humming-birds (Trochilida?), and the smaller 

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

 the sun-birds (Xectarineid^e) take the place of the humming- 

 birds, and another small group, the flower-peckers (Dica?ida?), 

 assist them. In the Australian region there are also tAvo 

 flower-feeding groups, the Meliphagida?, or honey -suckers, 

 and the brush -tongiied lories (TrichoglossidcT). 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 ^lexico, 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 TMs peculiarity of local distribution of colour in 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 

 the fertilising insects to avoid carrjdng the poUeu of one flower to the stigma 

 of a distinct species. 



