66 INTEGUMENTS OF PLANTS. 



cuticle of the hand and foot, or covering of the ox or tortoise, com- 

 pared with the membranes of the eye, etc. It peels off in the birch, 

 etc., as with animals, not possessing, as with them, vitality. It is 

 designed to protect the plant from external injury and to regulate 

 through its pores, perspiration and absorption, as with animals, yet 

 admitting light and heat, but excluding injurious substances. The 

 cuticle of rye, wheat and some grasses is valuable in the arts, espe- 

 cially in the manufacture of bonnets, for which the cellular texture is 

 removed, leaving the cuticle only. It contains, in many plants, silex 

 or flint, as in the reeds and scouring rush. It is the least destructible 

 part and often has upon it wool, or down, like that of animals and for 

 like purposes. 



The cellular integument or texture is next beneath the epidermis, 

 or cuticle, and contains a resinous fluid which, in young plants, is 

 commonly green. In this are the glands for decomposing the gases 

 and other materials for the growth of the plant. It is the true skin" 

 and the depository of color as in animals and man, alike in the white 

 Caucasian and the black African. In fruits this integument has vari- 

 ous colors. It dies on the surface like the cuticle. It often cleaves 

 off, but is renewed by the cambium, or descending sap. 



The cortex is directly beneath the cellular texture. It is formed of 

 longitudinal fibres, or cortical vessels which, forming every year, are 

 plainly seen in annular deposits, or rings, when a tree is cut down : 

 by these its age is determined. The particular qualities of plants 

 reside in their cortex. The resins, astringent principles, and the aro- 

 matic oils are found in it. The inner part, called the liber, is the seat 

 of the principle and vital functions of the plant. The name is from a 

 book, the leaves of which it resembles in its annual layers deposited 

 by the descending sap. It is a kind of net work resembling cloth. As 

 a new layer is formed, the old one of bark is pushed outward which 

 readily loses its vital principle and forms an inert crust. It is of 

 liber that cloth is made, a with flax, the paper-mulberry, etc. This 

 being the vital part of the plant, it cannot be destroyed with impunity. 

 The most recently formed part of the liber, between the wood and the 

 bark, remains inactive during the repose of vegetation. After effect- 

 ing the development of buds and the formation of new wood and bark 

 it hardens, as in previous years, and loses its vital power. Herbs 

 and shrubs generally have a larger portion of pith than trees, and 

 young vegetables more than old ones. The medullary rays diverge 

 from the centre to the circumference. They are fibrous textures inter- 

 woven in the wood; and new buds appear to originate where they 

 terminate on the exterior. 



The wood consists of the perfect wood and the alburnum or sapwood, 

 which is the outer new part, at first soft, but annually becoming hard. 

 As with perfect wood, new layers are formed yearly. Most of the sap 



