BARK. 



Sicily. It is used by glass-makers, soap- 

 boilers, bleachers, and in other manufac- 

 tures. 



BARK, in vegetable anatomy, a term 

 Which denotes the exterior part of vege- 

 table bodies; which is separable from the 

 other parts of the plant during- the sea- 

 son of vegetation, but at other times re- 

 quires maceration in water, or boiling; 

 and when detached by any of these 

 means, the fine connections which unite 

 it to the wood are destroyed. When bark 

 is thus separated, and seen by means of 

 the microscope, it exhibits parvs differing 

 much in structure and use. These have 

 been divided into the cuticle or epider- 

 mis, the cellular envelope or parenchy- 

 ma, and the cortical layer and liber. The 

 epidermis is a thin transparent membrane, 

 which covers all the outside of the bark.' 

 It is pretty tough. When inspected with 

 a microscope, it appears to be composed 

 of a number of slender fibres, crossing 

 each other, and forming a kind of net- 

 work. It seems even to consist of diffe- 

 rent thin retiform membranes, adhering 

 closely together. This, at least, is the 

 case with the epidermis of the birch, 

 which Mr. Duhamel separated into six 

 layers. The epidermis, when rubbed off, 

 is reproduced. In old trees it cracks and 

 decays, and new epidermis are succes- 

 sively formed. This is the reason that the 

 trunks of many old trees have a rough 

 surface. The parenchyma lies immedi- 

 ately below the epidermis ; it is of a deep 

 green colour, very tender and succulent. 

 When viewed with a microscope^ it seems 

 to be composed of fibres which cross 

 each other in every direction, like the 

 fibres which compose a net Both in it 

 and the epidermis there are numberless 

 interstices, which have been compared 

 to so many small bladders. The cortical 

 layers form the innermost part of the 

 bark, or that which is next to the wood. 

 They consist of several thin membranes, 

 lying the one above the other ; and their 

 number appears to increase with the age 

 of the plant. Each of these layers is com- 

 posed of longitudinal fibres, which sepa- 

 rate and approach each other alternately, 

 so as to form a kind of net-work. The 

 meshes of this net- work correspond in 

 each of the layers ; and they become small- 

 er and smaller in every layer as it ap- 

 proaches the wood. These meshes are 

 filled with a green-coloured cellular Sub- 

 stance, which has been compared by ana- 

 tomists to a number of bladders adhering 

 together, and communicating with each 

 other. 



The matter of the parenchyma, and the 



juices which exist in barks, vary extreme- 

 ly, and probably occasion most of the dif- 

 ferences between them. Some, as oak 

 bark, are characterized by their astrin- 

 gency, and contain tannin ; others, as cin- 

 namon, are aromatic, and contain an es- 

 sential oil ; others are bitter, as Jesuit's 

 bark ; some are chiefly mucilaginous, 

 others resinous, 8cc. 



1. Bark of the cinchona floribunda, or 

 quinquina of St. Domingo. This bark is 

 in rolled pieces, six or seven inches Jong, 

 and three or four lines in thickness. Its 

 colour is greyish green externally, but 

 within it exhibits different shades of 

 green, purple, white, brown, &c. "Its taste 

 is bitter and disagreeable ; its odour strong 

 and unpleasant. It gives out nearly half 

 its weight to water, provided it be boiled 

 in a sufficient quantity of that liquid. 

 The residue possesses the properties of 

 woody fibre. The decoction of the bark 

 has a reddish brown colour, and an ex- 

 tremely bitter taste. It deposits on cool- 

 ing a blackish substance, soft and tenaci- 

 ous, which does not dissolve in cold wa- 

 ter, though it is soluble in hot water and 

 in alcohol. More of this substance pre- 

 cipitates as the liquor is evaporated. 

 When the inspissated juice, freed from 

 its precipitate, is mixed with alcohol, a 

 quantity of gummy matter separates. 

 When the black matter, which precipi- 

 tates as the decoction cools, is treated 

 with hot alcohol, the greatest part of it 

 is dissolved; but a fine red powder re- 

 mains mixed with some mucilage, which 

 is easily separated by water. When the 

 alcoholic solution is exposed to the air, it 

 deposits light yellowish crystals of a saline 

 nature. When mixed with water, white 

 flakes are thrown down which possess the 

 properties of gluten ; but the greatest 

 part remains in solution. Thus the soluble 

 part of the bark may be separated into 

 five distinct substances; namely, gum, 

 gluten, a red powder, a saline matter, and 

 a brownish bitter substance, retained in 

 solution by the diluted alcohol. The last 

 is by far the most abundant. To it the 

 peculiar qualities of the decoction of this 

 bark are to be ascribed. 



2. Bark of cinchona officinalis. This 

 tree grows in Quito ; it is confined to the 

 high grounds, and when stripped of ita 

 bark soon dies. There are three different 

 kinds of bark to be found in commerce, 

 but whether they be all obtained from the 

 same trees is not known ; the contrary is 

 probable. The following are the most re- 

 markable of these varieties. Red Peru- 

 vian bark. This bark is usually in large 



