516 EXPERIMENTS ON THE ROOTS OF PLANTS. 



Society only a kind of preface to a more complete work. I have, 

 however, seen the phenomenon repeated with a sufficient number of 

 vegetables, and agree with the author whose theory of the rotation of 

 crops is the basis of my observations, in considering it nearly general, 

 at least among all the phanerogamous vegetables. 



Vigorous plants of Chondrilla tmiralis, when placed in rain water 

 filtered, having their roots first cleansed as I above described, vegetate and 

 bloom freely. These were thrown away when full blown, and replaced by 

 fresh ones every two days, to allow no time for a change of regimen. 

 After eight days, the water acquired a yellow tint and a strong odour 

 very similar to that of opium, and a bitter and rather a pungent taste; 

 it precipitated in small brown flakes the solution of sub -acetate and 

 neutral acetate of lead, rendered turbid a solution of gelatine, &c., and 

 by slow evaporation deposited a residuum of a brown -reddish colour, 

 which I shall examine hereafter, and which leaves no doubt that the 

 water was perfectly free from any observable substance whatever. In 

 order to ascertain whether this substance was produced or not from 

 the vegetation of roots, I steeped, during the same time, the roots only 

 of the Chondrilla, and in another phial, the stalks only, cut from the 

 same plant. They continued fresh and in flower, but the water was 

 not charged with any remarkable colour, had no taste, nor smell resem- 

 bling opium, did not precipitate the acetate of lead, arid contained 

 scarcely any thing in solution. It was now clear to me that the 

 produce obtained from the entire plant was the result of exudation 

 from the roots, which took place only while the vegetable followed its 

 natural course. The same experiments repeated on several other plants 

 produced similar results, as will be seen when I speak of the produce of 

 a small number of families which I have had time to examine. When 

 once assured that plants rejected by their roots the parts improper for 

 their nourishment, ^it remained for me to ascertain at what time of the 

 day the phenomenon took place. For that purpose I steeped a vigorous 

 plant of the kidney bean (Phaseolus vulgarif) with the root in rain 

 water during the day ; at night the plant was taken out, washed 

 carefully, dried, and replaced in another jug full of rain water : the 

 experiment continued eight days, the plant continuing to vegetate with 

 great vigour. On examining the two liquids, I found in both evident 

 marks of the excretion from the roots; but the water in which the 

 plant had vegetated during the night contained a considerably greater 

 quantity. Both were clear and transparent ; the experiment being 

 repeated many times on plants of different natures, produced always 



