50 THE FERTILISATION OF FLOWERS. [CHAP. 



pollen and shrivelled up, the stigmas mature. Self- 

 fertilisation cannot take place. The more conspicuous 

 these flowers are rendered by association, the larger 

 the number of insects by which they are visited. 



In Viburnum (Guelder Rose) the flowers are 

 arranged on a similar principle to the Umbellifers, 

 but the outer circle of flowers produce neither stamens 

 nor pistil, the corolla being developed to a very large 

 size instead. This has the effect of rendering the 

 flower-head very conspicuous, and, together with the 

 powerful perfume exhaled, is an attraction to the 

 insects, who ramble over the flowers collecting and 

 depositing pollen as they go. For this they are re- 

 warded with a plentiful supply of honey. 



/IN 



St 



FIG. 58. 



FIG. 59. 



FIG. 60. 



In the Composite order of plants we have a similar 

 arrangement, of which the Common Daisy may be 

 taken as a type. The "flower" of this plant is in 

 reality a cluster of flowers or " florets." The advan- 

 tages of this arrangement are (i) the flowers are 

 rendered more conspicuous ; (2) the honey is more 

 easily accessible from the close proximity of the 

 flowers, consequently more insects visit it; and (3) 



