156 APPENDAGES OF THE STEM. 



minor order of foliage usually seated at the base of 

 the proper leaves, in the near neighbourhood of the 

 buds, to which, perhaps, they are in some way neces- 

 sary. Their special use in the system is not, how- 

 ever, very apparent, though from their station they 

 may be necessary in some way or other to the matu- 

 ration of the buds. 



Spines, Prickles, Stings. These are called the 

 armature of plants. Spines originate in the wood, 

 as Pyrus, and seem to be abortive shoots. In Ulex 

 they are the extremities of the branches, and retain 

 their vitality for years. Prickles are produced on 

 the bark, or on the leaves, and have only a tem- 

 porary existence. Both these appendages are osten- 

 sibly for defence against browsing animals ; more 

 especially of those kinds of plants that are armed 

 when young, but lose their armature when grown up 

 and out of the reach of cattle : example, the white- 

 thorn. Some trees appear to be particularly guarded 

 against climbing animals, as Gledltschia horrida. 

 Many plants, as Mammallaria, are leafless, but pro- 

 fusely covered with spines ; these, probably, do the 

 office of leaves ; but other functions are attributed 

 to them, namely, that they are conductors of electric 

 'currents supposed to be especially necessary to these 

 plants. Stings, awns, hair, down, on the surface of 

 plants, are all appendages of the same nature, and 

 all necessary one way or other in the economy of 

 the vegetable. The hairs on some twining stems 

 are reflexed. 



