APPENDAGES OF THE STEM. 149 



separated by art. This idea is however controverted, 

 it being- held by many eminent physiologists, that 

 the new accretions are formed out of the elaborated 

 sap ; and particularly the new layer of alburnum, 

 which is every year added to the axis of the stem. 



In whichever light we view the different appear- 

 ance, state, or qualities of the sap of trees, &c., 

 whether as gum, resin, jelly, or water, it is perfectly 

 homogeneous ; and whether contained in the body 

 of the plant yielding it, or in the gallipots of the 

 druggist, it is always found free from any fibrous or 

 other matter that could possibly by combination form 

 the organic structure of a plant. We are, therefore, 

 we may again repeat, confirmed in opinion, that woody 

 structure and substance can no more start into exist- 

 ence without a rudimental basis, than that an entire tree 

 can be produced without either seed, cutting, or layer. 

 Vegetable growth is only distension, expansion, or 

 amplification of a rudimental membrane : and the 

 elements composing this membrane are increased by 

 the assimilating power of the organic apparatus of 

 the plant. 



Appendages of the stem. These are hybernacula 

 or bud covers, leaves, stipula, spines, prickles, ten- 

 drils, glands, awns, hair, downs, bractea, natural exu- 

 dations of the juices, and floral members. 



Hybernacula. As seeds have various coverings, 

 so buds, whether of leaves or flowers of shrubs and 

 trees, are protected during hybernation, or before 

 expansion, by an envelope of membranaceous leafits 



