436 CONSERVATIVE ORGANS. [LECT. VIU. 



to be chiefly reservoirs of the proper juice formed 

 by the first year's foliage, which is expended in 

 the formation and perfecting of the flower-stem 

 and the fructification, the productions of the second 

 year. 



As the growth of the flower-stem, therefore, 

 and the evolution of the flower advance, the root, 

 instead of increasing in bulk, gradually shrivels, 

 and becomes of a more ligneous texture, owing 

 to the absorption of the proper juice and to the 

 emptied state of the short tubes. On this account 

 we find that those biennial roots, the Carrot and 

 Turnep for example, in which the art of cultivation 

 has so much increased the deposition of nutritious 

 matter, as to render them important as articles of 

 food to man and other animals, cease to be fit for 

 this purpose very soon after the flowers of the 

 plants to which they belong make their appearance. 



The perennial herbaceous roots are still more 

 varied in structure, as far as regards the proportion 

 and arrangement of the vascular parts, than either 

 the annual or the biennial. It would be impossible 

 in this place to demonstrate even a very small pro- 

 portion of those diversities : and these roots have 

 been too little examined to admit of any classifi- 

 cation founded on structure. I shall venture, how- 

 ever, to arrange them into two classes, the first 

 comprehending those which, besides sap and pro- 

 per vessels, are composed chiefly of short tubular 



