148 PHYSIOLOGICAL VIEWS. ^ 



and air, while it excludes every substance which would be in. 

 jurious. 



It is to the cuticle of wheat, oats, rye, and some of the grass- 

 es, that we are indebted for straw and imitation Leghorn hats. 

 In their manufacture, the straws are scraped, so that nothing 

 remains but the cuticle. It has been ascertained that the outer 

 bark of many of the grasses contains silex, or flint ; in the 

 scouring rush, (Equisetum,) the quantity of silex is such, that 

 housekeepers find it an excellent substitute for sand, in scour- 

 ing wood or metals. A singular property of the cuticle is, 

 that it does not seem to be subject to the same changes as the 

 other parts of bodies ; it is, of all substances found upon ani- 

 mal or vegetable matter, the least 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 cuti- 

 cle covered with a kind of wool ; the pericarp of the peach 

 has a downy cuticle. 



2d. Cellular Integument, 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 carbonic acid gas, by re- 

 taining the carbon and evolving the oxygen gas. The cellular 

 integument envelopes branches, as well as trunks of trees, and 

 herbaceous stems; it extends into roots, but there it neither 

 remains its green colour nor decomposes carbonic acid gas. 

 It is the seat of colour, and in this respect analogous 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 In- 

 dian, 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 sur- 

 face in the form of the cuticle, and often cleaves off. It is re- 

 newed internally from the cambium. 



The petals of flowers are almost entirely composed of cellu- 

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

 refract and reflect the rays of light, so as to produce the bril- 

 liant and delicate tints which constitute so great a portion of 



Uses of the epidermis or cuticle Cellular integument Glands of the cellu- 

 lar integument Cellular integument in roots The seat of colour Cellular in- 

 tegument in leaves, &c. In aquatic plants How renewed in the trunks of 

 trees Found in the petals of flowers, <fcc. 



