218 M. Macaire on Vegetable Physiology, 



gelated in this manner very well for several days, the water was 

 tested by hydrosulphuret 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 dip- 

 ped into the pure water. Groundsel, cabbage, and other plants, 

 gave the same result. Some plants grew very well for two days 

 in acetate of lead. They were then withdrawn, their roots well 

 washed with distilled water, carefully wiped, again washed in 

 distilled water (which, being afterwards tested, was found to con- 

 tain 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, be- 

 ing less injurious 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 shewed the presence 

 of lime by oxalate of ammonia, and plants which had grown in 

 lime, and then transferred with every precaution to pure water, 

 soon disgorged into it a portion of lime. 



Similar trials were made with a weak solution of marine salt, 

 and with a like result. Learning from M. De Candolle that 

 marine plants, when transported in a healthy situation, frequent- 

 ly grow well at a distance from the sea, and that, in such cases, 

 the soil in which they grow contains more salt than the sur- 

 rounding soil, the author endeavoured to imitate nature by ta- 

 king a few common plants, placing their roots in rain-water, and 

 wetting their leaves with a solution of marine salt. None of the 

 salt was discoverable in the water ; and it may therefore be in- 

 ferred either that solutions of salt cannot imitate the delicate 

 process of nature, or perhaps more probably that soda plants 

 alone have the power of absorbing, by their leaves, marine salt, 

 and rejecting a portion of it by their roots. 



There can be no doubt, then, that plants have the power of 

 rejecting, by their roots, soluble salts, which are injurious to ve- 

 getation. The author gives a few interesting details of experi- 

 ments on some particular families of plants. 



Leguminous Plants.^-^The only plants which he tried of this 

 family were peas and beans. They live and grow well in pure 

 water. After some time, the liquid, being examined, has no sen- 



