202 



SPOTTED KNOTWEED. 



without benefiting the plant. To prevent the visits of the latter, therefore, the hairs 

 secrete a viscid fluid, which makes the stem slippery and difficult to climb. This 

 plant, as its name denotes, may live in the water. In that case it is safe against those 

 climbing pilferers, and then the stem is smooth, with no hairs and no sticky sub- 

 stance. The arrangement is a special one, and furnished only when needed in the 

 economy of the plant. 



