350 



FOUNDATIONS OF BOTANY 



of the bugloss (Fig. 247, b) ; sometimes they are decidedly- 

 barbed. If the barbs are well developed they may cause 

 the hairs to travel far into the flesh of animals and cause 

 intense pain. In the nettle (Fig. 247, a) the hairs are 

 efficient stings, with a brittle tip, which on breaking off 



Fig. 246. — Thorn 

 Stipules of Locust. 



FiQ. 2^.—JSv.p7u>rtia splendens. 



The spines are dead and dry 



stipules. 



exposes a sharp, jagged 

 tube full of irritating 



fluid. These tubular hairs, 



with their poisonous contents, 



will be found sticking in the 



skin of the hand or the face 

 after incautious contact with nettles, and the violent itching 

 which follows is only too familiar to most people. 



419. Cutting Leaves. — Some grasses and sedges are 

 generally avoided by cattle because of the sharp-cutting 

 edges of their leaves, which will readily slit the skin of 

 one's hand if they are drawn rapidly through the fingers. 

 Under the microscope the margins of such leaves are seen 

 to be regularly and thickly set with sharp teeth like those 

 of a saw (Fig. 247, c, d). 



