22 ON FLOWERS AND INSECTS. [LECT. 



accessible to a great variety of small insects. The union 

 of the florets into a head, moreover, not only renders 

 them more conspicuous, but also enables the insects to 

 visit a greater number of flowers in a given time. 



It might at first be supposed that in such small 

 flowers as these self-fertilisation would be almost un- 

 avoidable. In most cases, however, the stamens ripen 

 before the stigmas. 



The position of the honey on the surface of a more or 

 less flat disc renders it much more accessible than in 

 those cases in which it is situated at the end of a more 

 or less long tube. That of the Deadnettle, for instance, 

 is only accessible to certain humble bees ; while H. 

 Muller has recorded no less than seventy-three species 

 of insects as visiting the Common Chervil, and some 

 plants are frequented by even a larger number. 



In the Composites, to which the Common Daisy and 

 the Dandelion belong, the association of flowers is 

 carried so far, that a whole group of florets is ordi- 

 narily spoken of as one flower. Let us take, for in- 

 stance, the Common Feverfew, or large white Daisy 

 (Chrysanthemum parthenium, Figs. 20 22). Each 

 head consists of an outer row of female florets, in 

 which the tubular corolla terminates on its outer side in 

 a white leaf- ovary, which serves to make the flower more 

 conspicuous, and thus to attract insects. The central 

 florets are tubular, and make up the central yellow part 

 of the flower-head. Each of these florets contains a 

 circle of stamens, the upper portions of which are united 

 at their edges and at the top (Fig. 20), so as to form a 

 tube, within which is the pistil. The anthers open 

 inwards, so as to shed the pollen into this box, the lower 



