24 ON FLOWERS AND INSECTS. [lect. 



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. 22), 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 

 part of which is formed by the stigma, or upper part of 

 the pistil. As the latter elongates, it presses the pollen 

 against the upper part of the box, which at length is forced 

 open, and the pollen is pushed out (Fig. 23). Any insect 

 then alighting on the flower would carry off some of the 

 pollen adhering to its under side. The upper part of 

 the pistil terminates in two branches (Fig. 24, st), each of 

 which bears a little brush of hairs. These hairs serve to 

 brush the pollen out of the tube ; while in the tube the 

 two branches are pressed close together, but at a later 

 stage they separate, and thus expose the stigmatic sur- 

 faces (Fig. 23), on which an insect, coming from a 

 younger flower, could hardly fail to deposit some pollen. 

 The two stigmas in the ray florets of Parthenium have 

 no brush of hairs ; and they would be of no use, as these 

 flowers have no stamens. 



The Leguminosee, or Pea- tribe, present a number of 

 beautiful contrivances. Let us take a common little 

 Lotus corniculatus (Fig. 25). The petals are five in 

 number ; the upper one stands upright, and is known as 

 the standard (Fig. 26, std) ; the two lateral ones present 

 a slight resemblance to wings (Figs. 26, 27, w), while 

 the two lower ones are united along their edges so 



