530 



BOTANY OF THE LIVING PLANT 



Pollination. The tawny colour of the flower attracts wasps, which are 

 the pollinating agents. The flowers are strongly protogynous. While the 

 stamens are still tightly packed in the globose corolla, the stigma protrudes 

 so as to meet any visiting insect, and receives any pollen he may bring. Later 

 it is strongly recurved, and the stamens then straighten their filaments, 

 carrying their anthers outwards, partly blocking the lower side of the corolla- 

 tube. They will thus deposit their pollen on the ventral surface of the visit- 

 ing insect, conveniently for transfer to the stigma of flowers in the earlier 

 female stage. The posterior stamen from its position could not do this : it 



FIG. 436. 



Scrophularia nodosa. I. flower in anterior view with stigma removed, and 

 stamens dehiscent (late stage). II. same in section. III. flower seen laterally with 

 projecting stigma (early stage). IV. floral diagram. 



is superfluous, and is reduced to a staminode. Cross-pollination is thus highly 

 probable, but self-pollination is possible by pollen falling from the anthers 

 upon the still receptive stigma. 



The Foxglove (Digitalis purpurea, L.) has a similar structure, but its wide 

 bell is suitable for humble bees, the pollen being deposited on their backs. 

 The flowers are here protandrous. Cross-pollination is probable, but self- 

 pollination is still possible. Comparison of the Foxglove with the Fig wort 

 shows how, with the same plan of floral construction, there may be differences in 

 the detail and in the agent of cross-pollination. 



(39) The Germander Speedwell (Veronica Chamaedrys, L.) is a common 

 perennial of road-sides and banks. It has long ascending shoots bearing 

 decussate leaves. The racemose inflorescences arise in the axils of the upper 



