SECT. V. THE LIGNEOUS LAYERS. 341 



constitute the whole of the difference between the 

 fibres of the several organs of the plant. For they 

 are often also different in kind as well as in degree, 

 as may be exemplified in the fibres of the bark and 

 wood. If the fibres of the former are separated by 

 the destruction of a part, the part is again regene- 

 rated, and the fibres are again united, without leaving 

 behind them any traces of a wound. But if the fibres 

 of the latter are separated by the destruction of a 

 part, the part is never regenerated, and the fibres 

 are never united. 



CHAPTER III. 



ELEMENTARY OR VASCULAR ORGANS. 



FROM the previous analysis of the composite or- 

 gans it appears they are all ultimately reducible to 

 fibres, cellular tissue with or without parenchyma, 

 and reticulated membrane which we must con- 

 sequently regard as being, under one modification or 

 other, the ultimate and elementary organs of which 

 the whole mass of the plant is composed. If it is 

 asked of what the elementary organs are themselves 

 composed, the reply is they are composed, as ap- 

 pears from the same analysis, of a fine, colourless, 

 and transparent membrane, in which the eye, aided 

 by the assistance even of the best glasses, can dis- 

 cover no traces whatever of organization ; which 



