THE 



GARDENER'S MAGAZINE, 



DECEMBER, 1828. 



PART I. 



ORIGINAL CORRESPONDENCE. 



Art. I. Outlines of Horiiadtural Chemistry : — Vegetable 

 Physiology. By G. W. Johnson, Esq., of Great Totham, 



Essex. 



(,Continncdfromp.323.) 



Immediately beneath the bark is situated the 'wood, which 

 forms the chief bulk of trees and shrubs. It is formed of con- 

 centric layers, one at least of which is added annually. These 

 layers are formed of a tissue of longitudinal fibres, resembling 

 network, the interstices of which are filled up with soluble 

 matter, differing in each vegetable genus, but closely resem- 

 bling its parenchyma. The layer immediately in contact with 

 the bark, is the softest and palest in colour, and thence is called 

 the alburnum. It is in this that the vessels which convey the 

 sap from the roots to the leaves are chiefly situated. This 

 layer is annually renewed, that of the previous year becoming 

 more complete wood. Although the chief part of the sap- 

 vessels, as just observed, is situated in the alburnum, yet 

 others, though more scanty, are dispersed through the whole 

 of the wood. Wherever situated, they extend from the extre- 

 mity of the minutest root to the leaves. The idea that the 

 .annular layer of wood is rendered more dense and firm by 

 severe winters, is denied by reason, and demonstrated to be 

 false by actual observation. The layers are thickest on those 

 sides of a tree where the largest branches occur, and are, 

 throughout, of greater size in such years as afford the most 

 genial period to vegetation. 

 Vol. IV. — No. 17. gg 



