268 



BRITISH FLOWERING PLANTS 



CHAP. 



been observed by Vaucber in 1841, and in the genus 

 Oxabs by Jacquin, who regarded them as indicative of 

 diflerent species ; but it was reserved for the genius and 

 perseverance of Charles Darwin to explain ' the signifi- 

 cance of this curious phenomenon, and the important 

 part it plays in the economy of the flower. Now that 

 it has been pointed out, it is sufficiently obvious. 



An insect thrusting its proboscis down a Primrose 

 of the long-styled form (Fig. 168) would dust its pro- 

 boscis at a part which, when it visited a short-styled 

 flower (Fig. 169), would come just opposite the head of 



Fig. 168. Fig. 169. 



Fig. 168. — Primula farinosa. Long-styled form and pollen. 



Fig. 169. — Short-styled form and pollen. 

 (>, anthers ; ca, calyx ; co, corolla ; st, stigma. Pollen x 250. 



the pistil, and could not fail to deposit some of the 

 pollen on the stigma. Conversely, an insect visiting a 

 short-styled plant would dust its proboscis at a part 

 further from the tip, which, when the insect sub- 

 sequently visited a long-styled flower, would again 

 come just opposite the head of the pistil. Hence we 

 see by this beautiful arrangement, insects must carry 

 the pollen of the long-styled form to the short-styled, 

 and vice versa. 



There are other points in which the two forms difl'er 

 from one another ; for instance, the stigma of the long- 

 styled form is globular and rough, while that of the 

 short-styled is smoother and somewhat depressed. The 

 pollen of the two forms (Figs. 168 and 169) is also dis- 



' Journ. Linn. Son. {Bot.) vi. (1862). 



