ANATOMY Of VEGETABLES. 10S 



1. Epidermis. Every part of a living plant is cov- 

 ered with a skin or membrane, called tiie epidermis or 

 cuticle. 



The term cuticle has been applied by anatomists to 

 the scarf skin which covers the animal body. There is 

 the most striking analogy between the animal and veg- 

 etable cuticle. 



The cuticle is sometimes called the outer bark. 

 Upon the leaves and annual branches it is membranous 

 and transparent. Upon older branches it is more or 

 less opaque, and on the bodies of old trees it is coarse, 

 thick, cleft and scaling off, being sometimes altogether 

 removed, as in old oaks and elms, the dead layers of the 

 inner bark performing its functions. 



The Birch has its outer hark in circular layers re- 

 sembling paper, for which daat of- the White Birch has 

 heen used as a substitute. 



The outer bark serves (he purpose of protection from 

 external injuries, at the same time that it regulates the 

 proportion of absorption and perspiration through its 

 pores. It is destitute of vitality ; the only part of a 

 living plant which is dead. Although it does not grow, 

 yet it is capable of very great extension. 



The outer bark of many of the grasses, and of sev- 

 eral species of Equisdum or scouring 1 rush, contains 

 silicious earth or flint. It is so abundant in the Rat- 

 tan, that it will give fire with steel. 



2. The Cellular integument. Immediately beneath 

 the cuticle or outer bark we find the cellular iutegu- 

 ment. This being for the most part green, is the 

 seat of colour, and so far is analogous to the cutis or 

 true skin of animals. 



The leaf consists of an extension of the cellular in- 

 tegument, covered on both sides by a membranous ex- 

 pansion of the cuticle. It is of a succulent vascular na- 

 ture, and is important in a physiological point of view, 

 being the part in which the fluids are changed by the 



