CHAP. II. ARMATURE. 77 



presses it. This is the rationale of the stinging of the 

 Nettle. 



In Malpighia urem the sting is spindle-shaped, 

 laying parallel to the surface of the leaf and fixed to 

 it by the middle, the points being finely acuminated. 

 Whether it secretes a fluid which is discharged by 

 pressure, as in the sting of the Nettle, I have not 

 been able to ascertain, as I have never seen it except 

 in a dried state, and I do not recollect to have read 

 any account of it in its vegetating state. But even 

 in its dried state it is still troublesome enough to 

 any one that handles it, for the points having now 

 become stiff and rigid do the more readily pene- 

 trate the skin and fasten upon the hand that touches 

 them. 



Sometimes the organ of defence is a prickle, Prickles, 

 being a stiff and sharp-pointed process issuing from 

 the stem or branch and originating in the bark, 

 along with which it may be entirely stripped off. 

 In some plants it is straight and upright, forming an 

 acute angle with the upper part of the shoot or 

 branch, as in the young shoots of the Barberry ; in. 

 some it is also straight but issuing at right angles to 

 tbe shoot or branch, as in the Gooseberry ; in some 

 it is said to be spiral, as in the genus Hugonla ; in 

 some it is reflected, as in the genus Rosa (PL III. 

 Fig. 12.) ; and in some it is forked or divided, or 

 growing in sets of two, three, or more, as in the 

 Gooseberry and older branches of the Barberry. 



Sometimes the organ of defence is a thorn, being Thorns. 



