CHAP. III. ELEMENTARY ORGANS. 343 



tended that it is not likely they should contain such 

 cavity from their capability of indefinite division. 

 But the fact is, that the tubular structure of the 

 longitudinal fibres may be distinctly perceived, as 

 well as legitimately inferred, in the case both of her- 

 baceous and woody plants. 



If the stem of a plant of Marigold is divided by As disco- 

 means of a transverse section, the divided extremities the stem 



of the longitudinal fibres, arranged in a circular row 

 immediately within the bark, will be distinctly per- P lants - 

 ceived, and their tubular structure demonstrated by 

 means of the orifices which they present, particu- 

 larly when the stem has begun to wither.* The 

 same sort of structure may be observed in the stem 

 of cucurbitaceous plants also, particularly in that of 

 the Gourd, in which there are besides discoverable 

 several sets of longitudinal tubes situated near the 

 centre, and of considerable diameter. 



But it has been pretended that the above aper- Objec- 

 tures are not the orifices of vessels, because they do 

 not empty themselves when cut. This would not 

 be a very formidable argument if it were even the 

 fact, which it is not ; as there are many plants to 

 be met with whose vessels do empty themselves 

 when cut. If you cut or break asunder the stem of Answered. 

 any species of Spurge the vessels will immediately 

 begin to empty themselves on both surfaces formed 

 by the section or fracture ; and if the vessels do 

 not so empty themselves in all herbaceous plants, 

 * Vcntenat. Tab, du. Reg. Veg. vol. i. 



