II.] DIFFERENCES BETWEEN ALLIED SPECIES. 41 



Thus, as Miiller has pointed out, Malva sylvcstrii 

 (Fig. 43) and Malva rotundifolia (Fig. 44), which grow 

 in the same locahties, and therefore must come into 

 competition, are nevertheless nearly equally common. 

 In both species the young flower contains a pyramidal 

 group of stamens which surround the stigma, and 

 produce a large quantity of pollen, which cannot fail 

 to dust any insect visiting the flower for the sake of its 

 honey. In Malva sylvestris (Fig. 43), where thebranches 

 of the stigma are so arranged (Fig. 45), that the plant 

 cannot fertilise itself, the petals are large and conspi- 

 cuous, so that the plant is visited by numerous insects; 



FiG. 45. — Stamens and stigmas of Malva 

 sylvestris. 



Fig. 46.— Diltoof il/u/z-a rotundi/oliii. 



while in Malva rotundifulia (Fig. 44), the flowers of 

 which are comparatively small and rarely visited by 

 insects, the branches of the stigma are elongated 

 and twine themselves (Fig. 46) among the stamens, 

 so that the flower can hardly fail to fertilise itself. 



Another remarkable instance occurs in the genus 

 Epilobium, which is, moreover, specially interesting, 

 because in E. angustifoliiun, as I have already men- 



