82 THE EVOLUTIONIST AT LARGE. 



glossy leaves grow apace, and soon fill out, 

 not only with green chlorophyll, but also with 

 a sharp and pungent essence which makes 

 them burn the mouth like cayenne pepper. 

 This acrid juice has been acquired by the 

 plant as a defence against its enemies. Some 

 early ancestor of the arums must have been 

 liable to constant attacks from rabbits, goats, 

 or other herbivorous animals, and it 'has 

 adopted this means of repelling their ad- 

 vances. In other words, those arums which 

 were most palatable to the rabbits got eaten 

 up and destroyed, while those which were 

 nastiest survived, and handed down their pun- 

 gency to future generations. Just in the same 

 way nettles have acquired their sting and 

 thistles their prickles, which efficiently protect 

 them against all herbivores except the patient, 

 hungry donkey, who gratefully accepts them as 

 a sort of sauce piquante to the succulent stems. 

 And now the arum begins its great prepa- 

 rations for the act of flowering. Everybody 

 knows the general shape of the arum blossom 



