162 



THE STRUCTURE OF FLOWERS. 



spot from which to reach two drops of honey that seem to 

 rest upon a knee-shaped bend in the upper petals (a), the leaf 

 springs downwards (fe), and the stamen is set free and flies 

 upwards, dusting the lower surface of the insect with pollen. 

 When the stamen has thus served its purpose, it gradually 

 curves upwards out of the flower (c), and the style which was 

 hitherto undeveloped grows gradually out of the flower in a 

 horizontal direction, so as to form another alighting place (c)." 

 Rapid movements in the stamens are not unknown. 

 I described that of Medicago * many years ago, and now 

 supply figures. Fig. 49, a repre- 

 sents the front view of a flower on 

 expansion ; 6, the same after a bee 

 has exploded it — the staminal 

 column has now arisen, curled up- 

 wards, and abuts against the 

 standard; c shows the curved posi- 

 tion of the stamens, the corolla 

 being removed. The stamens are 

 inelastic, as they will not return to 

 a horizonal position without break- 

 ing across, if pressed downwards. 

 Many other rapid movements of the filaments are too well 

 known to need description, such as those of Berberis, Helian- 

 themiim, Sparmannia, Centaurea, and TJrtica ; while Orchids 

 exhibit various movements in the caudicles of their pollinia. 



Besides slow movements, the pistil often exhibits rapid 

 ones on being touched, as are known to occur in Stylidium, 

 Canna, Mar ant a and allied plants ; while the flap-like stigmas 

 of Mimulus^f and of several genera of orders allied to the 

 Scrophularineo}, close together on being irritated mechanically. 



* Journ. Lin. Soc, vol. ix. p. 327. 



t Mr. F. W. Oliver has lately investigated the mode of conduction 



Fig. 19.— Medicago sativa. (For de- 

 scription, see text ) 



