PHANEBOGAMIA. 



267 



lip usually serving as a resting-place for the insect -while it 

 thrusts its head or tongue into the corolla. The upper lip 

 is frequently arched so as to contain the stamens and style. 

 In the Dead-nettle the stigma projects beyond the stamens 

 (Fig. 145), so that upon visiting successive flowers the in- 

 insect always first pollinates the stigma with pollen from 



Fig. 146.— Flowers of Composites. A, of Dandelion, showing style protruding 

 througli ring of anthers; B, of Thoroughwort; C, ditto, vertical section showing 

 ^yle surrounded by anthers; D, style showing two stigmas. All magnified. 



preceding flowers, and then coming in contact with the 

 stamens secures more pollen. In many plants with a sim- 

 ilar structure the stamens mature before the stigmas are 

 ready for pollination, so that in these, while the means for 

 cross-pollination are perfect, self-fertilization is rendered 

 impossible. 



