1S2 OF THE FULCRA, 



Bot. t. 270, considers thorns as abortive buds, and 

 thence very ingeniously and satisfactorily accounts for 

 their disappearance whenever the tree receives more 

 nourishment. 



The permanent footstalks of the Gum Tragacanth 

 shrub, Astragalus Tragacantha^ are hardened into 

 real spines, as are the flower-stalks in Pisonia, as well 

 as the stipulas of Xanthhim spinosum and the Mimoscs. 

 — Linn. Mss. 



4. Aculeus,/, 121, a Prickle, arises from the bark only, 

 and comes off with it, having no connection with the 

 wood, as in Rosa, Riibus (the Bramble Raspberry, 

 t^c.),-An^Zizyphus, mild. Sp. PL v. 1, 1102. 



This is not liable to disappear by culture, being 

 very distinct in nature from the last. 



5. Cirrus, t. 9,/ 122. A Tendril. This is indeed 

 properlv called 'a fulcrum or support, being intended 

 solely to sustain weak and climbing stems upon more 

 firm and sturdy ones. By its means such climbers 

 often reach, in tropical forests, to the summits of lofty 

 trees which they crown with adventitious blossoms. 

 Tendrils or claspers when young are usually put forth 

 in a straight direction ; but they presently become 

 spiral, making several circumvolutions, by which 

 they take hold of any thing in their way, and then as- 

 sume a firmer texture. After accomplishing a cer- 

 tain number of turns in one direction, some tendrils 

 have a power of twining subsequently the contrary 

 way ; many of them moreover are branched or com. 



