LECT. III.] EPIDERMIS* 99 



a greater portion of surface ; but new cuticle is 

 added to produce this effect. 



The use of the epidermis is to keep the parts 

 beneath it together ; and to regulate the perspira- 

 tion and absorption of the plant. It is calculated 

 also to defend the parts it covers from humidity; 

 for which purpose, it is covered with a waxy secre- 

 tion. The powers of the cuticle in regulating these 

 functions is fixed according to the nature of the 

 plant. In succulent plants, which require much 

 moisture to be retained in their leaves, the cuticle 

 is so constructed as to assist absorption, but rather 

 to prevent transpiration. Thus, if a leaf of the Aloe 

 be cut off, it will remain a very long time, even 

 when exposed to the sun's rays, before it shrivels ; 

 but, if in this state it be exposed to damp air, or 

 thrown into water, the absorption is so rapid that 

 it will regain its original plumpness and size in a 

 few hours. A fine proof of that overruling Wisdom 

 which fits every thing for the fulfilment of the 

 purposes of its creation : for, in this instance, 

 the Aloe being a native of a dry arid soil, and a 

 warm climate, it could not long exist if the per- 

 spiration from the surfaces of its leaves were con- 

 siderable, but on the contrary it draws a great deal 

 of moisture from the atmosphere by absorption. 

 Another use of the epidermis is to prevent the 

 destruction of the parts it covers : for, as it is in 

 the vessels of the inner bark, as I will afterwards 



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