1029 



from the evaporation of their water ; and it was found that, in the 

 course of a few hours, it had absorbed a considerable quantity of the 

 solution, and its leaves had recovered their former freshness and state 

 of distension. Next day, this branch absorbed less of the solution 

 than on the preceding one, and the poisonous effects of the bichloride 

 were now visible some way up the stem, also the lower leaves were 

 partially attacked, having become discoloured and shrunken, but the 

 unaffected parts of these leaves and of the other portions of the 

 branch retained their natural freshness, and appeared quite healthy. 

 Thus the bichloride of mercury continued to destroy successive por- 

 tions of the branch from day to day ; those parts of it to which the 

 influence of the poison had not extended always remaining to all ap- 

 pearance sound, and in some cases distinguishable from the affected 

 ones by a line of demarcation more or less defined. 



" 8. After the solution had ascended into that part of the stem 

 which was soft and contained but little ligneous matter, its diameter 

 became very much contracted, from the collapsed state of its vessels 

 and ceils, and was rendered so flexible as to be incapable of support- 

 ing the sound parts above it, which, notwithstanding this altered and 

 contracted state of the inferior portion of the branch, seemed perfectly 

 healthy, and continued to receive an abundant supply of fluid. The 

 upper parts of this branch remained vegetating in the solution during 

 a fortnight, although the lower ones were completely deprived of every 

 trace of vitality, shewing that the passage of the fluid along the latter 

 into the former is wholly independent of any vital contraction of the 

 sap vessels, as was formerly supposed by the older physiologists. 



" 9. But in order to remove any doubt as to the correctness of this 

 conclusion, a stem of Valerian was obtained, from which grew two 

 long parallel branches of equal size, and a portion, fifteen inches in 

 length, of one of them, was exposed to the action of boiling water dur- 

 ing a quarter of an hour, after which the inferior extremity of the parent 

 stem was placed in a weak solution of the bichloride of mercury for a 

 fortnight. During this time the process of vegetation was found to bf» 

 quite as active in the upper part of the branch which had been acted 

 upon by the boiling water, as in that which had been carefully pro- 

 tected from the action of the heat." — p. 2. 



On repeating the first of these experiments Mr. Rainey found that 

 in some plants the process of vegetation ceased immediately on sepa- 

 rating them from their stems; others vegetate only at one p^od of 

 the year : he also found that in cases when a plant ceased to vegetate 

 in the bichloride it also ceased to vegetate in water : when a plant will 

 Vol. II. 6 n 



