342 ELEMENTARY ORGANS. CHAP. III. 



membrane we must also regard as constituting the 

 ultimate and fundamental fabric of the elementary 

 organs themselves, and by consequence of the whole 

 of the vegetable body. 



But though we have thus ascertained the ultimate 

 and elementary organs of the whole of the vegeta- 

 ble body, together with the primary fabric of which 

 they are themselves composed, we have not yet 

 finished our inquiries with respect to them. A 

 question or two remains yet to be instituted and 

 answered, with regard to the structure of the longi- 

 tudinal fibres. Are they tubular, or are they solid r 

 and if tubular, are they all of the same species ? 

 Longitu- It has been asked, indeed, by some phytologists 



dinal fibres 



tubular, whether or not plants are furnished with vessels 

 analogous to the blood vessels of the animal system. 

 But if it is admitted that plants contain fluids in 

 motion, which cannot possibly be denied, it will 

 follow as an unavoidable consequence that they 

 are furnished with vessels conducting or containing 

 such fluids. We have already seen that the pulp 

 and pith are composed of clusters of bags or blad- 

 ders, which are, at least in the young shoot or 

 plant, filled with a vegetable juice. But it is not 

 with regard to them that any doubt has existed ; 

 but with regard to the structure of the longitudinal 

 fibres, which some have described as tubular, and 

 others as solid. The latter have said that it is im- 

 possible to discover any tubular cavity in such fibres 

 even with the aid of the best glasses ; and have con- 



