28 



ON FLOWERS AND INSECTS. 



LECT. 



As the type of another class of cases in which two 

 kinds of flowers are produced by the same species (though 

 not on the same stock) we may take our common Cow- 

 slips and Primroses. If you examine a number of them, 

 you will find that they fall into two distinct series. In 

 some of the flowers, the pistil is as long as the tube, and 

 the button-shaped stigma (Fig. 31, st) is situated at the 

 mouth of the flower ; the stamens (a a) being half-way 

 down the tube : while in the other set, on the contrary, 

 the anthers are at the mouth of the flower, and the 



. OoOO 

 



X 250 



FIG. 31. Primula (long-styled form). FIG. 32. Primula (short-styled form). 



stigma half-way down. The existence of these two 

 kinds of flowers had long been known, but it remained 

 unexplained until Mr. Darwin devoted his attention to 

 the subject. Now that he has furnished us with the 

 clue, the case is clear enough. 



An insect visiting a plant of the short-styled form 

 would dust its proboscis at a certain distance from the 

 extremity (Fig. 32, a), which, when the insect passed to 

 a long-styled flower, would come just opposite to the 

 pistil (Fig. 31, si). At the same time, the stamens of 

 this second form (Fig. 31, a) would dust the proboscis at 



