262 SHADE PLANTS OF THE ALPINE FORESTS 



Swartz.), chiefly in certain peculiarities of the styles. 

 These three species are very nearly related, and are 

 often difficult to distinguish. The Serrated Winter- 

 green (Pyrola secunda, Linn.) is easily recognised by 

 the fact that all the flowers of the raceme or 

 inflorescence are turned to one side. The leaves are 

 also more strongly toothed than in the other species. 



The pollen-shedding mechanism of the Winter- 

 greens offers a very pretty study, and is worth investi- 

 gation. If we examine the pendulous flowers of 

 Pyrola secunda or P. rotundifolia, we shall find that 

 when they have just opened, the stalks of the stamens 

 are bent in an S-shaped manner, and are held in 

 position by the pressure of the petals. The stalks 

 are in a high state of tension, like a bent spring. At 

 this stage the tips of the anthers, where the pores are 

 placed, are directed towards the base of the flower. 

 When an insect visits the flower, and pushes back the 

 petals, the pressure on the spring-like stalk is released, 

 and it straightens out. The result is that the anther 

 performs a sort of somersault, turning through 180, 

 the tips now pointing to the mouth of the flower. 

 At the same time, the jerk caused by the release of 

 the spring shakes out a shower of pollen dust through 

 the pores on to the back of the insect. This process 

 can be imitated by simply pressing back the petals of 

 a flower in which the stamens are ripe, having first 

 carefully noted the position of the anthers in the 

 undisturbed condition. 



In the Single-flowered Wintergreen the arrange- 



