THORNS. PRICKLES. 135 



of Armenia ; it was first brought to this country 

 about two hundred and fifty years ago. 



The Sloe-tree, or Blackthorn, Pru'nus spino'sa, 

 in its natural state, is almost covered with thorns ; 

 indeed most of our fruit-trees, in their wild state, 

 are furnished with thorns; but cultivation soon 

 causes these to disappear, or greatly diminishes 

 their number. Thorns are, in fact, buds, which 

 a sufficient supply of food would convert into 

 branches and leaves, but whose growth is checked 

 for want of nourishment. In temperate climates 

 few vegetables are furnished with thorns ; but in 

 hot countries they render some of the forests 

 quite impenetrable. In some species of Mim'osa, 

 the thorns are so strong and thickly set, as to 

 form a complete defence against animals, except 

 such as have very thick and hard skins, like the 

 rhinoceros. 



Several plants are furnished with Prickles, which 

 are sometimes almost as stiff and sharp-pointed as 

 thorns; but there is this difference, that the prickle 

 springs from the outer bark, and may be peeled 

 off along with it, while the thorn grows from the 

 wood itself, and remains after the bark is taken 

 away. What we commonly call thorns in the 

 rose-bush, are only prickles. Grew remarks, that 

 " thorns being part of the wood, which has a ten- 

 " dency to grow upwards, generally point upwards 

 K 4 



