234 VEGETATION. [Lesson xxxiv. 



are now safely concealed under ground, preparing 

 their new shoots to burst forth when the earth is 

 softened in spring. Shrubs and trees which are ex- 

 posed to the open air have all their soft and ten- 

 der parts closely wrapt up in buds, which by their 

 firmness resist all the power of frosts ; the larger 

 kind of buds, and those which are almost ready to 

 expand, are farther guarded by a covering of resin 

 or gum, such as the horse-chesnut, the sycamore, 

 and the lime. Their external covering, however, 

 and the closeness of their internal texture, are of 

 themselves, as some say, not adequate to resist the 

 intense cold of a winter's night : a bud detached 

 from its stem, enclosed in glass, and thus protected 

 from all access of internal air, if suspended from a 

 tree during a sharp frost, will be entirely penetrated 

 and its parts deranged by the cold, while the buds 

 on the same tree will not have sustained the slight- 

 est injury: either the detached bud must have been 

 injured by reason of the cold entering it at the 

 part where it was broken from the stalk; or we 

 must attribute to the living principle in Vegetables, 

 the power of resisting cold to a very considerable 

 degree ; probably each of these is true in ome 

 measure; but how Vegetables require this latter- 

 mentioned property, must be left for future obser- 

 vations to determine. 



After the frost is moderated, and the earth suffi- 

 ciently thawed, the first vital function in trees is 

 the ascent of the sap, which is taken up by the ab- 

 sorbent vessels composing the inner bark of the 

 tree, and reaching to the extremity of the fibres of 



the 



