90 WONDERS OF PLANT LIFE 



into contact with the stinging hairs of the Nettle. 

 Under the microscope it is seen that these stings 

 consist of a long tapering cell, rising from a cushion- 

 like base. The point of the hairs is easily broken, 

 owing to the cell wall being very thin. When the 

 hair comes in contact with any object which the 

 apex can pierce, a slight wound is made, and at 

 the same time the upper part of the bristle breaks, 

 allowing the fluid which the cell contains to escape 

 into the opening. The poison, consisting as it 

 does of formic acid and a property known as 

 enzyme, is of a peculiarly irritating nature as 

 most people will have experienced to their cost. 



Far more formidable, however, are the stings 

 of certain exotic species, one of which, the great 

 Shrubby Nettle (Urtica crenulata] of Northern 

 India, is a really formidable plant. This species 

 attains to the height of fifteen feet, and is described 

 by Sir Joseph Hooker as having broad glossy 

 leaves covered with microscopic hairs. The plant 

 only seems to sting violently in the autumn, but 

 at that time the strength of the poison is such 

 that people have suffered from its effects for days. 

 Moreover, at the time of its greatest activity the 

 plant gives off an effluvia which is so powerful 

 that it causes running from the eyes and nose. 

 More formidable still is the Urtica gigantea of 



