THE CAMPANULAS 85 



are larger, and tlie flower-stalks less branched, and 

 bearing only one to five flowers on each plant. The 

 flower-buds droop in this species, whereas in the 

 Harebell they are almost erect. 



The flowers of either species are worthy of 

 examination. The drooping position of the corolla, 

 the mouth being directed downwards, serves both to 

 protect the pollen and to prevent the entrance of 

 unbidden guests (see p. 275) in the shape of crawling 

 insects, which serve no purpose useful to the plant. 

 For, to most Alpines, though not all, cross-fertilisa- 

 tion by means of insects, which carry the pollen or 

 male generative dust from one flower to fertilise the 

 female organs of another, is quite essential. In the 

 case of the Bell-flowers and the Rampions, we shall 

 find, if we examine the flowers, that a special 

 mechanism, termed the "mechanism of the stylar 

 brush," exists, which is adapted to ensure cross- 

 fertilisation, and also guards against the possibility 

 of self-fertilisation. Thus w^e see that an intimate 

 relationship and interdependence exists between 

 these plants and members of the insect world. We 

 shall later discuss other examples (p. 268). 



If we examine an unopened head of a very young 

 flower (Text-fig. VIIL, 1), dissecting away the corolla, 

 we shall find the five anthers of the stamens com- 

 pletely covering the style. The anthers at this stage 

 are united at their margins, though their stalks at the 

 base remain free. The nectar or honey, wdiich attracts 

 insects, is secreted by the ovary, which is completely 



