in Relation to Rotation of Crops. 219 



sible taste. Its smell is faintly herbaceous. It is quite clear, 

 and almost colourless, in the case of kidney-beans (haricots), 

 more yellow in peas and common beans (feves.) The fluid, 

 when examined by chemical tests, evaporation, &c. is found to 

 contain a matter very analogous to gum, and a little carbonate 

 of lime. 



It was found that when the water in which these plants had 

 lived was pretty well charged with this excrementitious matter, 

 fresh plants of the same species soon withered in it, and did not 

 live well. To ascertain whether this was for want of carbonic 

 acid in the fluid (which plants derive from the earth as well as 

 from the air), or from the presence of excreted matter, which 

 they repudiated, the author put into the fluid some plants of 

 another family, and especially wheat. This lived well, the yel- 

 low colour of the fluid became less intense, the residuum less 

 considerable, and it was evident that the new plant absorbed a 

 portion of the matter discharged by the first. It was a kind of 

 rotation experiment, performed in a bottle, and the result tends 

 to confirm the theory of De CandoUe. It is not impossible that, 

 by experiments of this kind, results may be obtained of practical 

 importance to agriculture. The author would infer that wheat 

 may follow with great advantage a crop of beans. 



Gramineous Plants, — Wheat, rye, and barley were examined. 

 They do not grow well in rain-water, probably from the nota- 

 ble quantity of mineral substances, especially silex, which they 

 contain, and which they cannot derive from pure water. The 

 water in which they have vegetated is clear, transparent, with- 

 out colour, smell, or taste. It contains some salts, alkaline, and 

 earthy muriates and carbonates, and only a very small portion 

 of gummy matter. He thinks these plants reject scarcely any 

 thing but the saline matters foreign to vegetation. 



^Chicoraceous Plants, — The CkondriUa muralis, and the 

 Sonchus oleraceus, live very well in rain-water. The latter ac- 

 quires a clear yellow colour, a strong smell, and a bitter taste. 

 Treated with tests, and concentrated by evaporation, it is found 

 to contain tannin, a brown gummo-extractive substance, and 

 some salts. 



Papaveraceous Plants. — Plants of field poppy (Papaver 

 Rh^tasJ will not live in rain-water; they speedily fade. The 



