vii Relations Between Plants and Animals 123 



painfully excited for some time afterwards. This property 

 is much exaggerated in some of its allies ; thus the 

 "Dumb-Cane" of the West Indies is associated with ugly 

 tales of slave-torture, and even nowadays with occasional 

 cruel practical joking among the usually gentle and kindly 

 race of gardeners. Even in Arum some acrid poison is 

 present, but the irritating effect is mainly due to the 

 myriads of minute needle-like crystals (the raphides of 

 old books on the microscope) which the plant's tissues 

 contain, and which pierce the soft skin of the experi- 

 menter's mouth. After this experience one remembers the 

 cuckoo-pint ; can you believe that the snails, which both 

 Darwin and Romanes credit with good memories, will 

 forget? For years a taste or a smell will remain in the 

 memory, and just as the suggestion of a mouthful of flinty 

 horsetails gives one a " goose-skin " shiver, so the snail on 

 a renewed impression of a disagreeable plant writhes its 

 horns in disgust and turns away. 



Stahl's research is doubtless valuable ; it is interesting 

 to know of the fifteen different kinds of protection which 

 save plants from being eaten by snails, though when he 

 says that he finds no wild flowering plant not even a tree 

 without some kind of protection against snails, the 

 suspicion cannot be repressed that he is proving a great 

 deal too much. And when he goes on to interpret these 

 protective qualities as being in direct relation to the appe- 

 tite of snails, to credit snails with being important factors 

 in the evolution of these qualities, we emphatically protest 

 against his conclusion. 



The notion is of course a familiar one, but the truth 

 that there is in it may be falsely exaggerated. Something 

 unusual happened within a plant and it became sour; the 

 snails tasted it and left it alone, but ate up its relatives 

 which remained sweet. These eaten up, the sour plant 



