BARK. ::3 



the surface of every vegetable. It is also called the cuticle, a name 

 which anatomists have given to the external covering of the animal 

 body. There is a striking analogy between animal and vegetable 

 cuticle or. skin. In the animal it varies in thickness from the deli- 

 cate film which covers the eye, to the thick skin of the hand or foot, 

 the coarser covering of the ox, or the hard shell of the tortoise. In 

 the vegetable, it is exquisitely delicate, as in the covering of a rose 

 leaf, or, hard and coarse, as in the rugged coats of the elm and oak. 

 In the birch you may see the cuticle or outer bark peeling off in cir- 

 cular pieces; it seems not to be endowed with the vital principle, and 

 in this respect differs from all other parts of tlif plant. The cuticle 

 serves for protection from external injuries, and regulates the pro- 

 portion of absorption and perspiration through its pores. It is trans- 

 parent as well as porous, so as to admit to the cellular integument 

 the free access of light and air, while it excludes every substance 

 which would be injurious. 



It is to the cuticle of wheat, oat, rye, and some of the grasses, that 

 we are indebted for straw and Leghorn hats. In their manufacture 

 the cellular texture is scraped away, so that nothing remains but 

 the cuticle. It has been ascertained that the outer bark of many of 

 the grasses contains silex, or fiint;— in the scouring rush, {Equise- 

 tuin^) the quantity of silex is such, that housekeepers find it an ex- 

 cellent substitute for sand, in scouring wood or metals. A peculiar 

 property of the cuticle is, that it is not subject to the same changes 

 as the other parts of bodies ; it is, of all substances found upon 

 animal or vegetable matter, the most indestructible. The cuticle is 

 sometimes, like the skin of animals, clothed with wool or down, and 

 it then becomes an important security against the effects of heat 

 and cold. The leaf of the mullein has its cuticle covered with a 

 kind of wool ; the pericarp of the peach has a downy cuticle. 



2d. CeUiilar Texture^ is situated beneath the epidermis or outer 

 skin of the bark ; it is filled with a resinous substance, which is 

 usually green in young plants. This cellular layer possesses glands, 

 which, when submitted to the action of light, carry on the process of 

 decomposing csrbonic acid gas, by retaining the carbon and evolv- 

 ing the oxygen gas. The cellular integument envelops branches, 

 as" well as trunks of trees, and herbaceous stems ; it extends into 

 roots, but there it neither retains its green colour, nor decomposes 

 carbonic acid gas. It is the seat of colour, and in this respect ana- 

 logous to the cutis, or true skin of animals, which is the substance 

 situated under the cuticle, and is black in the Negro, red in the 

 Indian, and pale in the American. In the leaves of" vegetables, the 

 cellular integument occupies the spaces comprised between the 

 nerves, and is of a green colour; in flowers and fruits it is of various 

 colours. The cellular substance of some aquatic plants is filled with 

 air; in the pine, sumach, &c., it is filled with the proper juices of the 

 plant. This herbaceous envelope of the trunks of trees, after a time, 

 dries, appearing on the surface in the form of a cuticle, and often 

 cleaves off. It is renewed internally from the cambium. 



The petals of flowers are almost entirely composed of cellular 

 texture, the cells of which are filled with juices fitted to refract and 

 reflect the rays of fight, so ^s to produce the brilliant and delicate 

 teints which constitute so great a portion of their beauty. The fuel, 



Uses of the eperdimis, or cuticle— Cellular texture— Glands of the cellular integu- 

 ment—Cellular integument in roots— The seat of colour— Cellular iiuegument in 

 leaves, &c.— In aquatic plants— How renewed in the trunks of trees— Found in the 

 oetals of flowers, &c. 

 10* 



