92 WONDERS OF PLANT LIFE 



There is little doubt that the development of 

 sour and poisonous juices in certain plants is 

 valuable as a protective measure. This is not 

 invariably so, for certain products such as the 

 tannin in the Oak are merely waste products 

 the outcome of a definite chemical process. Still 

 in the case of many species it is clear that the 

 plant derives a distinct advantage from its offen- 

 sive juice, and we can hardly regard its presence 

 as entirely accidental. If we take the strong- 

 tasting plants of the countryside the aromatic 

 Mint, the pungent Water Cress, the evil-smelling 

 Jack-in-the-hedge, to mention only three examples 

 we shall assuredly find that these species enjoy 

 a comparative immunity from attack. True 

 enough, as if by way of retaliation, certain insect 

 larvae seem to have developed a special fancy for 

 some of these species ; but, as a rule, the mild- 

 tasting vegetation is much more likely to receive 

 the attentions of marauders. 



A very interesting problem which arises in 

 connection with certain species of plants which 

 seem to be specially protected is that of mimicry. 

 The subject is one concerning which we have little 

 positive knowledge, yet some of the instances are 

 so striking that they cannot well be ignored. On 

 the face of it there is, of course, nothing pre- 



