340 COMPOSITE ORGANS. CHAP. IL 



they have acquired their utmost degree of solidity 

 and cohesion, which may be appreciated from the 

 solidity and cohesion of the wood which they form, 

 according to the weight that any given length and 

 diameter will sustain. When viewed under the 

 microscope they are generally transparent, and par- 

 ticularly at their points of inosculation. But in some 

 plants they are much finer than in others ; or the 

 bundles they form are smaller, as well as the meshes 

 of the net- work they compose, varying in their 

 aspect and properties in almost every species ; and 

 yet exhibiting a peculiarity of character that is 

 always uniform. Hence the carpenter can dis- 

 tinguish the different species of timber by inspect- 

 ing the surface of the section or fissure, with as 

 much facility as the botanist can distinguish the dif- 

 ferent species of plants by regarding their external 

 habit. 



As well But the quality of the fibres is not invariably the 

 differing same throughout all the different organs of the 



I" fabric^ P lant In the leaf the y Bre m re delicate than in 



the stem, and in the flower they are more delicate 

 than in the leaf. And yet this is not more than what 

 might have been expected from the analogy of the 

 vegetable to that of the animal in the applicability of 

 its different organs to the functions they are to per- 

 form the nerves or organs of sensation in the 

 animal being much more delicate in their fabric than 

 the muscles by which a limb is extended. 



And yet, delicacy or strength of fabric does not 



