in.] THE FERTILISATION OF FLOWERS. 



in passing over the flower-head one insect fertilises 

 several florets. There are nearly ten thousand known 

 species of this order, but the structure of the flower 

 is tolerably uniform, and can be well observed in the 

 Daisy or Feverfew. In the latter the stamens are 

 united so as to form a tube, enclosing the pistil. The 

 pistil is furnished at top with a brush of hairs. The 

 anthers ripen before the stigmas, and shed the pollen 

 on their inner surface, so that it is deposited in the 

 tube on the top of the immature stigmas which it 

 cannot affect. The pistil as it ripens elongates and 

 pushes up the pollen, which is thus brought in the 

 way of insects. By means of the brush every pollen 

 grain is swept out before the stigmas ripen. When 

 this has been effected, the stigmas raise themselves 

 from the tube, and assume a position as in fig. 60. 



FIG. 61. 



FIG. 62. 



FIG. 63. 



The flowers of the various species of Harebell 

 (Campanula) are more or less inverted, and among 

 the most graceful objects of our native flora. At first 

 both pistil and stamens are immature, the stamens 

 clasping the pistil (fig. 61). The anthers ripen, shed 

 their pollen on the style, and shrivel up. Insects 

 visiting the flower clasp the style, and thus remove 

 the pollen. The pistil then elongates, and the stigmas 



