OR APPENDAGES OF PLANTS. 223 



in A tract if lis cancellata. Linnseus observes 

 that no bracteas are to be found in the 

 class Tetradynamia. 



The ochrea of Rottboll, Willdeno<rs 

 Principles of Botany, 50, which enfolds 

 the flower-stalks in Cyperus, see Engl 

 Hot. t. 1309, seems to me a species of 

 brae tea, 



3\ Spina. A Thorn. This proceeds from 

 the wood itself, and is either terminal like 

 Hippophae rkamnoidss, Engl Bot. t. 425, 

 Rhammts catharticus, t. 1629 ; or lateral 

 as Crataegus (or Mespiius) Crus-galli, 

 tomentosa, parvifolia, &c. 



Linnaeus observes that this sometimes 

 disappears by culture, as in the Pear-tree, 

 Pyrus sativa, which when wild has strong 

 thorns ; hence he denominates such culti- 

 vated plants tamed, or deprived of their 

 natural ferocity. Professor Willdenow, 

 Principles of Bot. 270, considers thorns as 

 abortive buds, and thence very ingeniously 

 and satisfactorily accounts for their disap- 

 pearance whenever the tree receives more 

 nourishment. 



