14 ON FLOWERS AND INSECTS. [LECT. 



cannot fertilise itself, the petals are large and conspi- 

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

 while in Malva rotundifolia the flowers of which are 

 comparatively small and rarely visited by insects, the 

 branches of the stigma are elongated, and twine them- 

 selves (Fig. 10) among the stamens, so that the flower 

 readily fertilises itself. 



Another interesting case is afforded by the genus 

 Epilobium. Epilobium angustifolium has large purplish 

 flowers in conspicuous heads (Fig. 11), and is much 

 frequented by insects ; while E. parviftorum (Fig. 12) 



FIG. II. Epilobium angustifolium. FIG. 12. Epilobium parviflorum. 



has small solitary flowers and is seldom visited by 

 insects. Now in the former species their visits are 

 necessary, because the stamens ripen and shed their 

 pollen before the pistil, so that the flower is con- 

 sequently incapable of fertilising itself. In E. parvi- 

 florum, on the contrary, the stamens and pistil come to 

 maturity at the same time. 



Let us take another case that of certain Geraniums. 

 In G. pratense all the stamens open, shed their pollen, 

 and wither away before the pistil comes to maturity. 



