38 THE FERTILISATION OF FLOWERS. [cuap. 
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 ithe 
a 5 
Fie. 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- 
