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not vegetate either in the bichloride or in water its leaves wither from 

 the evaporation of their moisture, the plant not possessing the power 

 to absorb more fluid, thus showing that mere evaporation is insufficient 

 to cause the ascent of sap. When plants retain their vitality in the 

 bichloride the quantity absorbed is in proportion to the vigour of the 

 leaves, proving the ascent of sap to be dependent on some vital ope- 

 ration. No bichloride can be found in the portion of any branch 

 situated above the junction of the dead and living portions, which 

 both stems and leaves below this contain abundance, so that as the 

 water which suppled the living part " was derived from the solution, 

 a process of decomposition of the bichloride must have been continu- 

 ally going on at the union of the dead with the living part of the 

 branch all the time it was vegetating in the solution, by which the 

 bichloride is converted into pro-chloride and chlorine, the former, 

 being insoluble, remains in the vegetable tissue, whilst the latter, 

 being set free, is indicated by the change which it produces in the 

 colour of the plant; the water of this portion of the solution being 

 thus freed of all its bichloride, ascends into the living parts of the 

 branch to nourish them, and in this manner they receive their supply 

 of water from this poisonous solution the same as if the extremity of 

 the branch had been kept in water, or the entire plant had been de- 

 riving it from the soil on which it grew : so that a plant, whilst vege- 

 tating in a solution of the bichloride of mercury, may be distinguished 

 into three parts, the living, the dying, and the part completely dead ; 

 the first contains the water of the solution deprived of all its bichloride, 

 the second the portion of solution in which the bichloride is in the act 

 of being decomposed, and the third the solution unchanged." 



" 13. Now, as in the plants thus treated, the water of the solution, 

 which had been taken up into and nourished the living part of each 

 branch, was in reality its crude sap ; and as the same passages which • 

 conveyed this water, now deprived of its bichloride, must have con- 

 tained the solution whilst this substance was undergoing decomposi- 

 tion, and therefore whilst it contained some of the bichloride un- 

 changed ; to detei-mine the part along which the crude sap ascends, 

 we have only to ascertain the precise situation of the bichloride of 

 mercury and the tissue in which it is lodged." — ^5. 5. 



The author next explains an experiment in which the bichloride 

 has been converted into an insoluble bisulphuret by a reference to 

 plates which we cannot transfer to our pages ; and concludes this 

 branch of the inquiry by some remarks on the quantity of intercellu- 

 lar tissue contained in different parts of the same plant, and on the 



