THE STYLAR BRUSH MECHANISM 87 



pretty sure, when seeking the nectar, to come in 

 contact with the stylar brush, and to dust its head 

 with pollen, which it carries to another flower. If 

 the anthers have not all begun to curve, the touch of 

 the insect proboscis will cause them to bend 

 backwards. 



In a still older flower, the style, with the brush, has 

 greatly elongated and further has opened at the tip 

 into three little flaps, which curve slightly backwards 

 (Text-fig. VIIL, 3). It is on the upper or newly 

 exposed faces of these flaps that the stigmatic surface 

 lies, on which the pollen from another flower is 

 deposited by an insect visitor. The pollen fertilises 

 the ovules in the ovary below. The five stamens at 

 this stage are coiled into tight spirals. 



We see that by this arrangement self-fertilisation 

 is almost impossible. The pollen on the stylar brush 

 cannot reach the stigmatic surfaces above it, except 

 by insect agency, and an insect visiting a flower is 

 likely to touch the stigmas with pollen brought from 

 another plant, as it enters the flower; while, as it 

 leaves, the projecting flaps prevent the pollen of the 

 same flower being deposited on the stigmatic surfaces. 



The mechanism of the stylar brush is found not 

 only throughout the order Campanulacese, but also in 

 the very large family of Composites. It is, however, 

 most favourably studied in the Bell-flowers on account 

 of the comparatively large size of the organs. 



If we should find ourselves among the Alps in late 

 summer or in autumn, the fruits of the Campanulas or 



