238 



that's it ; 



nutiaB ; and, although they do 

 not affect the great outlines of 

 composition, they are all-import- 

 ant to colour and effect. 



The variety of mosses — the 

 green, which tinges the trunk of 

 the beech; the brimstone-coloured 



I have often stood with admiration before an 

 old forest oak, examining the various tints 

 which have enriched its furrowed stem. The 

 genuine bark of an oak is of an ash-colour, 

 though it is difficult to distinguish any part of 

 it from the mosses that overspread it ; for no 

 oak, I suppose, was ever without a greater or a 

 less proportion of these picturesque appendages. 

 The lower parts, about the roots, are often 

 possessed of that green velvet moss which in a 

 still greater degree commonly occupies the bole 

 of the beech ; though the beauty and brilliancy 

 of it lose much when in decay. As the trunk 

 rises, you see the brimstone colour taking 

 possession in patches. Of this there are two 

 principal kinds ; a smooth sort, which spreads 

 like a scarf over the bark; and a rougher sort, 

 which hangs in little rich knots and fringes. I 

 call it a brimstone hue, by way of general 

 distinction ; but it sometimes inclines to an 

 olive ; and sometimes to a light green. Inter- 

 mixed with these mosses, you often find a 

 species perfectly white. This white moss is 

 esteemed a certain mark of age, and where it 

 prevails in any degree, is a clear indication that 

 the vigour of the tree is declining. But there 

 are some situations where the moss becomes 

 white, not from the decline of the tree, but. 

 from external circumstances — as when the 

 trees grow very closely together, and there 

 is consequently a stagnated and damp atmo- 

 sphere surrounding it. We find, also, ano- 

 ther species of moss of a dark brown colour, 

 inclining nearly to black ; another of an ashy 

 colour, another of a dingy yellow. We may 

 observe also touches of red ; and sometimes, but 

 rarely, a bright yellow, which is like a gleam of 

 sunshine : and in m:my trees you vvili see one 

 species growing upon another, the knotted i 



and black, which stain the oak ; 

 and the yellow, which is fre- 

 quently found on the elm and 

 ash, are among the most beau- 

 tiful of those tints which em- 

 bo Uish the bark of trees. 



brimstone coloured fringe clinging to a lighter 

 species ; or black softening into red. Strictly 

 speaking, many of these excrescences, which I 

 have mentioned under the general name of 

 mosses, are classed by botanists under the 

 name of lichens.* 



These lichens, 14, are a large 

 and important order of plants 

 of low organization ; they form 

 large and irregular patches upon 

 the trunks of trees, surfaces of 

 rocks, &c., where they appear 

 more like the debris of decayed 

 matter, than what they really 

 are — new and living organisms. 

 Their substance is wholly com- 

 posed of cells, 543, without any 

 vessels, 543, and the membranous 

 expansion of which they con- 

 sist, assumes various forms, some- 

 times a concave or a convex disc ; 

 at other times cone-shaped, or 

 cup-like bodies. 



The use of these plants, in the great scheme 

 of nature, may be thus explained. They are 

 the pioneers of the higher orders of vege- ; 



* G.! in a Purest Scenery. 



13 



