CHAPTER III. 

 OF THE ELEMENTARY STRUCTURE OF PLANTS 



66. When we examine yet more closely, into the conforma- 

 tion of the different parts, of which an organised structure is 

 composed, we find that, though the several organs are variously 

 constructed, and are adapted for different offices or functions, 

 they are built up, as it were, of the same materials. With the 

 same bricks, stones, mortar, and timbers, a church, a palace, or 

 a prison may be reared. Just so is it in organised structures. 

 We do not find that each organ is entirely different from the 

 rest, though it has usually something peculiar to it ; but we are 

 enabled to separate it into many distinct portions, something 

 similar to which, if not exactly correspondent, may be recognised 

 in other parts, Thus, for example, it was formerly stated, that 

 the leaf consists of a midrib and veins proceeding from it, a fleshy 

 substance filling up the interstices, and a cuticle or skin covering 

 the whole. Now the midrib and veins, as well as the footstalk 

 of which these are a prolongation, consist of three kinds of struc- 

 ture ; woody fibre, to which they owe their toughness, and by 

 which they are adapted to give support to the softer structures ; 

 ducts or canals, for the transmission of fluid ; and spiral 

 vessels, which are designed to convey air. On tracing these to 

 fhe stem, it will be found that they all exist in it under the same 

 form, and that these portions of the leaves are in reality but con- 

 tinuations of it. Again, if we examine the fleshy substance 

 which lies amongst them, we shall find that it corresponds very 

 closely in character with the pulp of soft fruits, or the pith of the 

 stem. And if we strip off the cuticle and investigate its struc- 

 ture, we shall perceive that it is but another form of the same 

 kind of substance, and that it corresponds with the skin which 



