of Vegetable Membrane and Fibre. 425 



Now it will be found upon examination that the vesicles of 

 the cellular tissue are formed, with comparatively few excep- 

 tions, of membrane only, and though "vascular tissue," as 

 Professor Henslow observes*, "consists of tubes which are 

 also formed of membrane to all appearance identical with that 

 which composes the vesicles of cellular tissue" yet with respect 

 to the " true vessels or long tubes which more strictly com- 

 pose the vascular tissue," we find in the particular case of 

 spiral vessels, that the membrane is so slight, that " if a ves- 

 sel be ruptured and the spiral fibre uncoiled, no trace of the 

 membrane is to be seen excepting towards the conical ex- 

 tremity of the vessel, and also where the successive coils are 

 not in contact with each other f. 



It therefore appears to follow that membrane may be iso- 

 lated by obtaining the more common form of cellular tissuej, 

 where the walls of the cells are not " lined externally with 

 fibre," and then evaporating the fluid matter contained in the 

 cells; and also, that spiral vessels, entirely divested of the 

 cellular tissue in which they are generally imbedded, form the 

 nearest practicable approximation to isolated^Z>r£ §. 



In order then to obtain these materials in a state fit for 

 chemical analysis I had recourse to the roots of a hyacinth 

 grown in water. Each root consists of a central column of 

 spiral vessels surrounded by cellular tissue. When the plant is 

 young, the spiral vessels, having a diameter of about the j^th 

 of an inch, are not easily separable, even by boiling, from the 

 tissue in which they lie. But when the plant has arrived at 

 maturity, the entire column of spiral vessels having now, in 

 many instances, a diameter of nearly the ^jo^ 1 °f an inch ||, 

 as well as a considerable increase in the width of the spiral 

 thread, may by a little management (in fact, by simply rub- 

 bing the root between the fingers and the palm of the hand), 

 and without boiling, be readily drawn out of its sheath of cellular 

 tissue ; and each vessel is so free from any admixture of cel- 



* Principles of Botany, p. 20. t Ibid., p. 21. 



% " Membranous cellular tissue is that in which the sides consist of 

 membrane only, without any trace of fibre; it is the most common, and 

 was, till lately, supposed to be the only kind that exists." — Lindley's In- 

 troduction, p. 8. 



§ " In the root of the hyacinth the coils of the spiral vessel touch each 

 other, except towards its extremities." — Lindley's Introd., p. 19. 



|| " It is an axiom in vegetable physiology, that a part once fully formed 

 is incapable of any subsequent change. Thus, pith never alters its dimen- 

 sions, after the medullary sheath that incloses it has been once completed." 

 — Lindley's Introd., p. 33. 



This being the case, the larger vessels must have a later formation, 

 and the number of vessels in the young and old roots ought to indicate 

 this fact. 



Third Series. Vol. 11. No. 69. Nov. 1837. 3 I 



