II.] MOVEMENTS OF STAMENS AND PISTIL. 41 



Menyanthes, and Polygonum. It will be observed 

 that these genera belong to very different groups, 

 while on the other hand, in several cases, as in 

 Primula itself (Scott, " Proc. Linn. Soc." vol. viii.), we 

 find monomorphous and heteromorphous species in 

 the same genus. 



Another point of great interest is the spontaneous 



FIG. 40. Geranium pratense. 



movement of the stamens and pistil in dichogamous 

 plants, first observed by Kolreuter in Ruta graveo- 

 lens; he, however, supposed that the object was to 

 bring the stamens in contact with the pistil ; whereas 

 the real advantage, as Sprengel pointed out, is that 

 in consequence the stamens and pistil successively 

 occupy the same spot in the flower, and thus come in 



