Centaurea Cyanus. 73 



on a second similar one, equally beset round its margin 

 with down-curved points. 



The Centawrm, cyanus IL., which I have just taken 

 as an example of one statement, is of interest also in a 

 second way; for it serves to show that the question 

 whether the visits of animals are advantageous or pre- 

 judicial to a flower, depends not merely on the shape 

 of the animal that visits it, hut also upon the path by 

 which the animal makes its entrance. I have already, 

 at page 25, referred to this very noteworthy fact ; but 

 this will be a proper place to consider the structural 

 arrangements in plants which are therewith associated. 

 For this purpose it will not be necessary to start with 

 a detailed description of the flower-structure of Cen- 

 taurea cyanus. It will be enough to say that its 

 flowers are proterandrous and adapted for allogamy. 

 The upper part of the style, which in the earlier stage 

 of the flowering process sweeps out the pollen from 

 the anther-tube, and at a later stage lays bare the 

 receptive stigmatic surfaces, projects 4 mm. beyond 

 the tube of the corolla, and is so placed that even 

 small insects, if they come flying from above or from 

 the side, must inevitably graze it on their way to 

 the nectar; but should these small insects, on the 

 contrary, reach the flower from below, they would be 

 able to get at the nectar— which is so abundant as to 

 fill the bell-shaped expansion of the tube half-way up — 



without ever coming into contact with the stigma, 



G 



