OF THORNS. 261 



CHAPTER I. 



OF THORNS. 



I here designate under the general name of Thorns 

 {Armd) all the organs, or parts of organs, which de- 

 generate into a hard and more or less sharp point, and 

 which become kinds of defensive arms for the plants 

 furnished with them. It has been usual to distinguish 

 them into spines and prickles; but this distinction is less 

 easy than was at first thought. It has for a long time 

 been said, that spines proceed from the wood and 

 prickles from the bark ; but from this definition it must 

 be admitted, that only one of the organs exists in 

 Monocotyledons, where the wood and bark cannot be 

 distinguished, and one would even be puzzled to say 

 whether they belonged to spines or prickles ; in Di- 

 cotyledons themselves, there has been uncertainty in 

 knowing to which class ought to be referred the thorns 

 of several leaves, and those which grow upon the 

 flower and fruit. 



In this state of the science, I have remarked that 

 all the organs of plants are capable of taking, at their 

 extremities, a degree of induration which transforms 

 them into thorns ; and it has been easy to see that 

 those, which, until then, had received the name of 

 Prickles (Aculei), rather from some vague analogy 

 than from any strict definition, were organs of the 

 nature of hairs, indurated and larger than ordinary, and 

 that all the organs transformed into prickles came to be, 

 and have been, generally considered as Spines (Spinas). 



