VII.] 



BEE OPHRYS. 



175 



the position of the stigma, are nearly the same, but 

 the stalks of the pollen masses are long, thin, flexible, 

 and too weak to stand upright. The distance of the 

 pollen masses from one another, and the shape of 

 the pollen grains is moreover variable. The anther 

 cells open soon after the flower expands, and the 

 pear-shaped pollen masses drop out, so as to hang 

 directly over the stigma, with which a breath of air 

 is sufficient to bring them in contact. While there- 

 fore in most species of Orchis and Ophrys, self-fertilis- 



FIG. 124. Ophrys a f if era. 



ation appears to be impossible, in the Bee Ophrys, 

 as R. Brown long ago pointed out (Trans. Linn. Soc., 

 v. xvi.) it is carefully provided for. Darwin has 

 examined hundreds of flowers, and has never seen 

 reason in a single instance to believe that pollen had 

 been brought from one flower to another; and he 



