VEGETABLE STRUCTURE. 9 



scattered filaments more or less opaque. The entirely 

 closed cavities have been called Cellules or Utricles ; 

 the tubes, Vessels ; and the filaments, Fibres. 



If we now survey the various opinions which have 

 been formed upon the structure or general organization 

 of vegetables, we see that all the systems of phytotomists 

 may be reduced to three principal ones. Some, after 

 the example of Theophrastus, and perhaps of Grew, 

 have thought that all the vegetable tissue is formed of 

 very minute fibres differently interwoven. Others — 

 and Mu'bel appears to be the first who ventured the 

 opinion in a general manner — believe that it is a per- 

 fectly continuous membrane, the various doublings of 

 which produce the closed or tubular spaces which we 

 observe. Lastly, most modern observers, following that 

 which appears to have been the opinion of Malpighi, 

 admit that vegetables are essentially composed of Cel- 

 lules or Utricles differently joined together, and of 

 Vessels, which, by different modes of development and 

 cohesion, form all the organs. 



The comparison of these three theories will naturally 

 lead to the exposition of the facts upon which we are 

 about to enter ; passing in review — 



1st, The Cellular Tissue. 



2d, The Vessels, 



3d, That which is called the Fibre of plants. 



4th, The Epidermis, or Cuticle, which covers all 

 this apparatus. 



