SOME PLANT MARRIAGES 



445 



insects. Numbers of such flowers take a lateral direction, and are un- 

 provided with landing-stages ; for humming-birds never alight when 

 feeding, but sip the nectar as they hover with widespread wings at the 

 mouths of the flowers. The absence of ridges, knobs, and fringes, which 

 serve so useful a purpose in insect-pollinated flowers, is also to be remarked. 

 Darwin, in his Cross and Self-fertilization of Plants, gives an interesting 

 summary of the cases of bird-pollination known to himself, which it will be 

 useful to quote. " In South Brazil," he says, " humming-birds fertilize the 

 various species of Abutilon, which are sterile without their aid. Long- 

 beaked humming-birds visit the flowers of Brugmansia, whilst some of the 

 short-beaked species often penetrate its large corolla in order to obtain 

 the nectar in an illegitimate manner, in the same way as do bees in all parts 

 of the world. It appears, indeed, that the beaks of humming-birds are 

 specially adapted to the various kinds of flowers which they visit ; on the 

 Cordillera they suck the Salvics, and lacerate the flowers of the Tacsonice 

 and in Nicaragua Mr. Belt saw them sucking the flowers of Marcgravia 

 and Erythrina, and thus they carried pollen from flower to flower. In 

 North America they are said to frequent the flowers of Impatiens. I may 

 add that I often saw in Chili a Mimuswith its head yellow with pollen from, 



FIG. 549. YARROW (Achillea ptarmica). 

 A small Composite that is specially attractive to the little bees of the genus Prosopis. 



