METHODS OF POLLINATION 



cross-pollination by insects, but Darwin has shown that in some 

 of them the pollen of the long stamens is impotent or weak on 

 the short pistil of the same flower, but is prepotent on the long 

 pistil of another flower, and so the pollen of the short stamens 

 is prepotent on the short pistil of a different flower. 



307. Flowers in which the stamens mature first. This 

 is shown in the great willow herb or fire weed(Epilobium) . When 

 the stamens are mature the four stigmas are closed and the style 



Fig. 143. 



Proterandry (anthers mature before stigma) in the bellflower (Campanula). Left figure 

 shows the united stamens surrounding the immature style and stigma. Middle figure shows 

 the immature stigma being pushed through the tube and brushing out the pollen; while in the 

 right-hand figure, after the pollen has disappeared, the lobes of the stigma open out to receive 

 pollen from another flower. 



is bent backward. Later when the anthers have shed their pollen, 

 the style straightens out, and the stigmas open and become recep- 

 tive. In the evening primrose also ((Enothera biennis=Onagra 

 biennis} the stamens mature first (see paragraph 251). The 

 same is true of the high mallow with purple flowers. The sta- 

 mens are erect, shed their pollen, then wither and become 

 recurved, after which the styles elongate and the stigmas become 

 receptive. In most of the composite flowers the stamens mature 

 first (see the study of the sunflower, paragraphs 266-273). In the 

 bell-flower (Campanula) (fig. 143) the stamens are joined by their 

 anthers into a tube, and mature their pollen before the stigma, 

 which is inside the tube, is receptive and open. The stigma 



