134 Horticultural Chemistry. 



in solid matters : the first obtain nourishment by decomposing 

 the carbonic acid gas of the atmosphere, the latter do so in a 

 much smaller proportion ; hence the reason why the latter are 

 so much more impoverishing crops than the former, inasmuch 

 as that they acquire nearly all their solid matter by means of 

 their roots. These observations explain the conflicting state- 

 ments of Saussure and Hassenfratz on this point : the former 

 experimented with broad-leaved plants, the latter on such as 

 have small foliage ; the first maintained that plants increase 

 in solid content when their roots are supplied with water 

 only, the latter denied the fact. It has been advanced that 

 water is the sole food of plants ; but all experiments are incon- 

 clusive which are presented as supporting the theory. In the 

 first place, all waters contain earthy, saline, and organic mat- 

 ters ; even distilled water is not pure, as Sir H. Davy has 

 proved, and rain-water Margraaf has demonstrated to be much 

 less so. No plants, growing in water only, will ever perfect 

 seed ; and the facts, that different plants affect different soils, 

 and that a soil will not bear through a series of years the 

 same crop, whereas it will a rotation of different ones, demon- 

 strate that they each take different kinds of food from the 

 earth, and not that universal one, water, which is ever present 

 and renewed. 



Silica, or the pure substance of flint, is present in all soils ; 

 it is soluble in water, requiring one thousand times its weight 

 of this liquid to dissolve it (Kirwan's Mineralogy, vol. i. 

 p. 10.) ; it is found in many plants, and in all the grasses that 

 have been analysed. Alumina, or the basis of clay, present 

 in all soils, is so soluble in water as to be inseparable by the 

 filter, and is much more so when any of the acids are present 

 (Sennebier's Physiolog. Veget., vol. iiL p. 18.); it is found in 

 plants in minute quantities, especially in the grain of barley, 

 oats, wheat, &c. (Schrceder in Geklen's Journ., vol. iii. p. 525.) 

 Lime is found in almost all soils; it is easily soluble in 

 water, and there is but one plant which is known to contain 

 none of it as a constituent, the Salsola Soda. (Ann. de Chimie, 

 vol. xviii. p. 76.) Magnesia, generally present in soils, is 

 soluble in water, and is found in many plants. Iron is pre- 

 sent in all soils, in all natural waters, and in all 'plants. 

 Manganese is found in some soils ; it is soluble in water con- 

 taining acids, Sec, and is found in a few plants. But none 

 of these, in a state of purity, either simply or combined, have 

 ever been found capable of perfecting a plant through all its 

 stages of growth, when moistened with distilled water; the 

 contrary was the case, however, when the water contained in 



