CHARACEiE. 85 



(though I have samples before me now that shew it) ; there- 

 fore the fluid which passes between the vesicles must be 

 very small in quantity, and is so limpid as to be difficult to 

 discover." 



In what way the removal or injury of the granules, placed, 

 according to Mr. Varley, on the outer surface of the mem- 

 brane can influence or govern the circulation carried on 

 within that membrane, it is difficult to conceive. It seems 

 to me, that the anastomosing of the currents can only be 

 accounted for by adopting the view of Mr. Slack, relative to 

 the internal organization of the Characece to be mentioned 

 presently, or by supposing the internal membrane to be 

 ruptured in the situation of the boundary line, thus permit- 

 ting an escape of the circulating fluids from the interior of 

 the membrane to its exterior, and so deranging the dis- 

 position of the granules. 



Within the membrane which has been just described is the 

 proper circulating fluid of the plant, which, in full motion, is 

 dense and thick, though transparent, containing a variable 

 number of solid granules, which circulate with it in the 

 course already indicated from left to right. The granules 

 do not, however, all move with equal velocity, or in a pro- 

 cession as it were. 



Internal to this fluid, and occupying the centre or axis 

 of the cell is another fluid, almost quiescent, and usually free 

 from solid admixture. This is generally greater in quantity 

 than the former or circulating fluid. 



" These two fluids being of diflerent densities," accord- 

 ing to Mr. Yarley, " do not when the plant is in health 

 mingle, and are not separated by a membrane. According 

 to Mr. Slack, however, a membrane does exist between the 

 different fluids, enveloping the central, and forming an 

 axis for the circulating fluid to revolve on, usually becoming 

 attached in the course of the longitudinal boundary lines, 

 thus separating the two currents of the circulating fluid 

 from each other. It can now be understood in what way 

 injury to this membrane, if it really exist, would occasion the 



G 3 



