THE PLANT AND ITS ENEMIES 91 



Australia, which grows into huge bushes twenty 

 feet or more in circumference. It has been 

 pointed out by Mr. Edward Step that in the 

 foliage of the Common Elm very similar processes 

 to the stinging hairs of the Nettle are to be 

 observed. These are nothing like so formidable 

 as those of the Nettle, but are sufficiently so to 

 cause an annoying irritation to the hands. Of 

 course, the Elm is classed with the same natural 

 order as the Nettle. It seems likely that these 

 stinging hairs serve a real purpose in protecting 

 the young growths of the Elm just at a time when 

 they would be most likely to be damaged by 

 grazing animals. 



A singular development is that to be seen in 

 the case of the Cuckoo Pint (Arum maculatum). 

 In this case the tissue of the foliage contains 

 thousands of little crystal needles (in addition to 

 a certain acrid poison) which stick into the lips, 

 causing an intolerable burning sensation. This 

 fact may be proved by anyone biting a small 

 portion of the leaf. Whether these crystals are 

 really a protective measure or not, there is no 

 doubt that the plant must often be left alone on 

 account of their presence. The crystals are devel- 

 oped to a much greater extent in the case of 

 certain tropical plants allied to the Arum. 



