XVIl] CROSS-POLLINATION 165 



receptacle (subsequently the edible part) may be of the 

 following kinds ; the </ flowers, chiefly in the upper parts, 

 the short-styled $ flowers and the long-styled $ flowers, 

 chiefly in the lower parts of the hollow floral axis. There 

 are, moreover, two kinds of Fig-trees : one bearing the 

 ordinary figs, and another which bears barren or inedible 

 figs, containing only ^ flowers and more or fewer short- 

 styled % flowers. This barren fig is termed the Caprijicus. 



A certain species of Gall-wasp visits these inedible 

 figs and becomes dusted with pollen from the cT flowers 

 in its attempts to pierce the short-styled $ flowers, in 

 which it lays its eggs. It then dies. The hatched-out 

 wasp then creeps out of the fig, and becomes dusted with 

 pollen from the </ flowers as it does so. Thus laden it 

 flies to one of the ordinary figs to repeat the process. 

 Here, however, the long-styled $ flowers escape its 

 ravages, being protected by their long styles, and only 

 the short-styled flowers can be pierced and galled by the 

 wasp. During its evolutions, however, the wasp trans- 

 fers pollen to some of the long-styled flowers and these 

 eventually set seed and the receptacle ripens to an edible 

 fig. There are other curious details, but the principle is 

 illustrated by the above. 



The Broom (Sarothanmus) (Fig. 121) affords a very 

 instructive illustration of floral mechanism. The standard 

 is marked by dark lines leading from its lower part, 

 down the claw, and so to the base of the ovary : in the 

 Laburnum these dark lines lead at once to the honey 

 secreted at the base of the standard, but here there is no 

 honey. Nevertheless bees visit the flowers and obtain 

 pollen as their reward. 



The long style, enclosed in the stiff tube of ten 

 stamens, projects into the keel, so that the stigma and 

 the anthers of the longer stamens reach the beak-like 



