90 SYLVA AMERICANA. 



totally extinguished ; while the solid mass of the plant exposed 

 to the chemical action of surrounding substances, to which it now 

 yields, withers and dies away, presenting to the eye a decayed 

 and rotten appearance, and crumbling into dust from which it 

 originally sprang. Such is the transient duration of the vegetable, 

 and counterpart of animal life. 



Explanation of Plate I. 



Fig. 1 . A transverse section of a branch of ash, as it appears 

 to the eye. 



Fig. 2. The same section magnified. A, the bark. B, the 

 wood. C, the pith, o, the cuticle, b, an arched ring of sap 

 vessels next the cuticle, cc, the cellular substance of the bark 

 with its cells, and other arched rings of sap vessels, d, a circular 

 line of lymph ducts, immediately below the above arched ring, 

 e, the liber, h, the first year's growth, g, the second. /, the 

 third year's growth, k, the great air vessels. 7, the small ones. 



Fig. 3. Anatomy of wood after Mirbel, magnified, a, the 

 cellular texture. The membraneous sides of all these cells and 

 tubes, are very thin, more or less transparent, often porous, 

 variously perforated or torn. 5, a bundle of entire vessels 

 without perforations, c, tubes pierced with holes ranged in a 

 close spiral line, d, tubes having several of these holes running 

 together, as it were, into interrupted spiral clefts, e, tubes, which, 

 in some young branches and tender leaves, will unroll to a con- 

 siderable extent, when they are gently torn asunder. 



Fig. 4. A garden bean (Viciafaba), laid open, showing 

 its two cotyledons, f, the radicle, or that part of the corculum 

 which afterwards forms the root ; g, the corculum or germ. 



Fig. 5. A bean which has made some progress in vegetation, 

 showing the descending root, the ascending plumula and skin 

 of the seed bursting irregularly. 



