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substances which the willow contained, except water, may have 
been derived from the rain water, the earth in the pot, and the 
moisture imbibed from the surrounding soil. 
The experiments of Duhamel and Tillet are equally incon- 
clusive ; so that it is impossible for them to decide the question, 
whether water be the sole nourishment of plants or not ? But 
all the attempts hitherto made to raise plants from pure water 
have failed ; the plants vegetating only for a certain time, and 
never perfecting their seeds. These experiments were made by 
Hassenfratz, Saussure, and others, with the same unfavourable 
result. Duhamel found that an oak, which he had raised by 
water from an acorn, made less and less progress every year, 
AVe see, too, that those bulbous roots, such as hyacinths, tulips, 
&c. which are made to grow in water, unless they be planted 
in the earth every other year, refuse at last to flower, and even 
to vegetate; especially if they produce new bulbous roots an- 
nually, and the old ones decay. From all these facts and exper- 
iments, it is reasonable to conclude that water is not the sole 
food of plants 
So far, indeed, is water from being tlie sole food of plants, 
that in general, only a certain proportion of it is serviceable, 
too much being equally prejudicial to them as too little. 
Some plants, it is true, grow constantly in water, and will not 
vegetate in any other situation ; but the rest are entirely de- 
stroyed when kept immersed in that fluid beyond a certain 
time, 3Iost plants require a certain degree of moisture in or- 
der to vegetate well. This is one reason why different soils are 
required for different plants. Rice, for instance, requires a 
very wet soil : were we to sow it in the ground on which wheat 
grows luxuriantly it would not succeed : and wheat, on the con- 
trary would rot in the rice ground. AVe should therefore in 
choosing a soil proper for the ])lants which we mean to raise, 
consider the quantity of moisture which is best adapted for 
them, and choose our soil accordingly. Now the dryness or 
moisture of a soil depends upon two things ; the nature and 
proportions of the earths which compose it, and the quantity of 
rain which falls upon it. Every soil contains at least three 
earths, silica, lime, and alumina, and sometimes also magne- 
sia. The silica is always in a state of sand. Now soils retain 
moisture longer or shorter according to the proportions of these 
