150 Scientific Intelligence. [March, 



contained matter which had exuded from the roots. He satisfied himself that this 

 is the fact with respect to nearly all those plants which display their flowers. 



" Several plants of Chondrilla muralis, perfectly clean, were placed with their 

 roots in pure water. At the end of a week, the water was yellowish, and emitted 

 an odour like opium, and had a bitter taste. Subacetate and acetate of lead 

 produced a brownish flocculent precipitate, and a solution of gelatine disturbed its 

 transparency. As a proof that this matter was an exudation from the roots, it 

 was found that neither pieces of the root nor of the stem, when macerated in the 

 water during the same time, occasioned either taste, smell, or precipitate. 



" To prove that plants employ the excretory power of their roots, in order to 

 get rid of hurtful substances which they may have imbibed, the following experi- 

 ments were made. Some plants of the Mercnrialis annua were washed in distilled 

 water, and placed so that one portion of their roots dipped into a weak solution of 

 acetate of lead, and another branch of the same root into pure water. Having 

 vegetated in this manner very well for several days, the water was tested by hydro- 

 sulphuret of ammonia, which proved, by the black precipitate which it formed, 

 that a notable portion of the lead had been absorbed, and deposited by the branch 

 which dipped into the water. Groundsel, cabbage, and other plants, gave the same 

 results. Some plants grew very well for two days in acetate of lead. They were 

 then withdrawn, their roots well washed with distilled water, which being after- 

 wards tested, was found to contain no lead, and then placed to vegetate in rain 

 water. In the course of two days this water was found to contain a small quantity 

 of acetate of lead. 



" The same experiments were made with lime-water, which, being less injuri- 

 ous to plants, is preferable to lead. The roots being partly placed in lime-water, 

 and partly in pure water, the plants lived well, and the pure water soon showed 

 the presence of lime by the oxalate of ammonia ; and the plants which had grown 

 in lime, and were then transferred with every precaution to pure water, soon dis- 

 gorged into it a portion of lime. 



" Similar results were made with a weak solution of marine salt, and with a 

 like result. There can be no doubt, then, that plants have the power of rejecting 

 by their roots, soluble salts, which are injurious to vegetation. Experiments also 

 proved, that the roots exuded a greater excess of matter under night, than in the 

 day. As it is well known that the light of day causes the roots to absorb their 

 juices, it is natural to suppose that, during the night, absorption ceases, and ex- 

 cretion takes place." 



Some of the inferences which M. Macaire would deduce from his experiments, 

 are, that the greater number of vegetables exude by their roots substances unfit 

 for taeir vegetation ; that the nature of these substances varies according to the 

 families of plants which produce them ; and that some being acrid and resinous, 

 may be injurious ; and others, being mild and gummy, may assist in the nourish- 

 ment of other plants. 



But the most interesting experiments to an agriculturist, were made by M. 

 Macaire, with the bean, wheat, and potatoe. 



The bean lives well in pure water, which continues quite clear, but assumes a 

 yellow colour. Chemical tests and evaporation detect a matter in this water, very 

 analogous to gum, and a little carbonate of lime. It was found that the water in 

 which the bean had lived, was well charged with excrementitious matter. Fresh 

 plants of beans did not live well in it ; but to ascertain whether this arose from 

 want of carbonic acid in the fluid, or from the presence of exuded matter which 



