CHAP. II. ROOT. 255 



of the Physical Society of Geneva, has given an account of 

 his important experiments, of which the following is an 

 abstract : — He found that Chondrilla muralis, and Cichorace- 

 ous plants in general, seci'eted a matter analogovis to opium; 

 Leguminous plants, a substance similar to gum, with a little 

 carbonate of lime ; Grasses, a minute quantity of matter con- 

 sisting of alcaline and earthy muriates and carbonates, with 

 very little gum ; Papaveraceous plants, a matter analogous to 

 opium ; and Euphorbias, a whitish yellow gum, and resinous 

 matter of an acrid taste. 



He also found that plants actually possess the power of 

 freeino; themselves from matter that is deleterious to them, 

 by means of their roots. Acetate of lead is a well-known active 

 vegetable poison ; he took two bottles, one of which. A, was 

 filled with pure water, and the other, B, with water holding 

 acetate of lead in solution. He placed a plant of Mercurialis 

 annua with half its roots plunged in A, and the other half 

 in B. After a short time the water in the bottle A 

 contained a notable proportion of acetate of lead, which must 

 have been carried into the system by the roots in bottle B, 

 and thrown off again by those in bottle A. He also states 

 that various plants which had lain several days in water 

 charged with lime, or acetate of lead, or nitrate of silver, or 

 common salt, in small quantity, having been carefully washed 

 and placed in pure water, gave back from their roots the 

 deleterious matter they had absorbed. 



It is difficult to speculate upon the results to which this cu- 

 rious discovei-y may lead. It is in all probability an explanation 

 of the necesssity of the rotation of crops, of the action 

 of what are called weeds, of the utility of changing the earth 

 of plants growing in pots, and of other phenomena which could 

 not previously be accounted for. It requires, however, a 

 great deal of ulterior examination ; but as the enquiry has 

 been taken up by Dr. Daubeny, the learned Professor of 

 Botany and Chemistry at Oxford, at the instance of the 

 British Association, it is not to be doubted that a few years 

 will throw much additional light upon the 'subject. 



