38 THE FERTILISATION OF FLOWERS. [CHAP. 



great quantities must be lost in transit by being 

 blown in a direction where there are no other trees 

 of the species, or by falling to the ground. Therefore 

 it is necessary that very large quantities should be 

 produced to ensure that the small amount requisite 

 for fertilisation should reach its proper destination. 

 But in flowers fertilised by insects no such risk is run, 

 therefore only a small amount of pollen is produced. 

 Then, too, we find a marked difference in the 

 stigma of a wind-fertilised as compared with an 

 insect-fertilised plant, which will be best explained 

 by reference to these diagrams. Fig. 45 shows the 

 stigmas of Wheat and Hop, which are anemophilous; 

 fig. 46 those of the Primrose and Heath, which are 

 entomophilous. In fig. 45 it will be observed the 



FIG. 46. 



stigmas are more branched and hairy, the object, of 

 course, being to offer a larger surface to catch the 

 wind-borne pollen grains. In fig. 46, of insect-fer- 

 tilised plants, the stigmas are of a simpler form. 

 We have remarked that the colours of flowers are 

 for the attraction of insects, and to prove this we 

 must show that insects are sensible to colour. The 

 experiments of Sir John Lubbock, who has added so 

 much to our knowledge of insects, show this conclu- 



