THE SOLID COMPONENTS OF PLANTS. 237 



The Epidermis is that portion of the vegetable 

 structure which is exterior to all the others ; at least to 

 those which retain their vitality in the vegetating state 

 of the plant : or, it is that part which is interposed be- 

 tween the living organs of the individual, and all ex- 

 traneous substances. In this respect it resembles the 

 cuticle of animals ; it extends over the surface of every 

 part of the plant ; from that of the delicate petal of 

 the flower, to that of the leaves, the branches, the 

 stem, and the root; but, except in young stems and 

 roots, it is not the exterior part of those organs of the 

 plant ; the coarse rugged surface of older roots and 

 stems being exterior to the real epidermis. It is com- 

 mon to every kind of plant, nor can any exist without 

 it. The vegetable epidermis may be separated from 

 the parts, which it covers, by raising it cautiously with 

 a knife ; but this is more easily effected by macera- 

 tion and boiling. It is more readily separated from 

 the cellular substance it covers in the leaf, than in any 

 other part of the plant ; and for this purpose I would 

 recommend to the student the leaf of any of the Lily 

 tribe, before the stem shoots up ; or of the Lettuce or 

 Sorrel ; but even in these, some of the cellular matter 

 is always detached in separating it ; and to this cir- 

 cumstance is perhaps to be attributed the variety of 

 opinions which phytologists have advanced regarding 

 its structure. 



The epidermis appears at first of a green color on 

 the young stems and branches of almost all plants ; 

 but it changes to different hues, according to the age 

 of the part it covers. According to Du Hamel, it 

 is composed of fine, but tough fibres, which are inter- 

 woven together ; and everywhere interspersed with 

 pores, which permit the mouths of the absorbing, traus- 



iratory, and air vessels to open to thp atmosphere. 



Ir. Bauer, concieves its structure to be altogether 



