42 THE VITAL FUNCTIONS. 



ficially effected in the laboratory of the chemist, 

 it has been found that gum and sugar are inter- 

 mediate products, or states of transition between 

 various others ; and they appear to be peculiarly 

 calculated, from their great solubility, for being 

 easily conveyed from one organ to another. Starch, 

 and lignin, on the other hand, are compounds of 

 a more permanent character, and especially 

 adapted for being retained in the organs. Starch 

 which, though solid, still possesses considerable 

 solubility, is peculiarly fitted for being applied 

 to the purposes of nourishment : it is accord- 

 ingly hoarded in magazines, with a view to 

 future employment, being to vegetables, what 

 the fat is to annuals, a resource for the exigencies 

 that may subsequently arise. With this inten- 

 tion, it is carefully stored in small cells, the coats 

 of which protect it from the immediate dissolving 

 action of the surrounding watery sap, but allow of 

 the penetration of this fluid, and of its solution, 

 when the demands of the system require it. The 

 tuberous root of the potatoe, that invaluable gift 

 of Providence to the human race, is a remark- 

 able example of a magazine of nutritive matter 

 of this kind. 



The lignin, on the contrary, is deposited with 

 the intention of forming a permanent part of the 

 vegetable structure, constituting the basis of the 

 woody fibre, and giving mechanical support and 

 strength to the whole fabric of the plant. These 



