II.] MOVEMENTS OF STAMENS AND PISTIL. 37 



the other hand, in several cases, as in Primula itself 

 (Scott, Proc. Linn. Soc. vol. viii.), we find monomor- 

 phous and heteromorphous species in the same genus. 

 Another point of great interest, is the spontaneous 

 movement of the stamens and pistil in dichogamous 

 plants, first observed by Kolreuter in Riita graveo- 

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

 biing the stamens in contact with the pistil ; whereas 

 the real advantage, as Sprengel pointed out, is that 



I ■^/:ih'iY^\<^ ^ 



FiG. 41. — Geranium praieiise (young FiG. 42. — Geraniujn prateTise (older 



flower;. Five of the stamens are flower). The stamens have retired, 



erect. and the stigmas are expanded. 



in consequence the stamens and pistil successively 

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

 contact with the same part of the insect. For instance, 

 in Gcrauiiun pratense (Fig. 40), when the flower first 

 opens, the stamens lie on the petals, at right angles 

 with the upright pistils. As, however, they come to 

 maturity they raise themselves (Fig. 41 a), parallel and 

 close to the pistil (Fig. 41 b), which, however, is not as 

 yet capable of fertilisation. After they have shed their 

 pollen, they return to their original position (Fig. 42), 



