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physiologist sowed three seeds of the pea in the 
same kind of soil : one he suffered to remain ex- 
posed to the free air ; the other he inclosed in a 
tube of glass ; and the third in a tube of wood. 
The pea in the tube of glass sprouted, and grew in 
a manner scarcely at all different from that under 
usual circumstances ; but the plant in the tube of 
wood, deprived of light, became white and slender, 
and grew to a much greater height. 
The plants growing in a soil incapable of sup- 
plying them with sufficient manure, or dead orga- 
nized matter, are generally very low, having brown 
or dark green leaves ; and their woody fibre abounds 
in earth. Those vegetating in peaty soils, or in 
lands too copiously supplied with animal or vege- 
table matter, rapidly expand, produce large bright 
green leaves, abound in sap, and generally blossom 
prematurely. 
Where a land is too rich for corn, it is not an 
uncommon practice to cut down the first stalks, as 
by these means its exuberance is corrected, and it 
is less likely to fall before the grain is ripe ; excess 
of poverty, or of richness, is almost equally fatal to 
the hopes of the farmer ; and the true constitution 
of the soil for the best crop is that in which the 
earthy materials, the moisture and manure, are 
properly associated ; and in which the decompos- 
able vegetable or animal matter does not exceed 
one-fourth of the weight of the earthy constituents. 
The canker, or erosion of the bark and wood, is 
a disease produced often in trees by a poverty of 
soil ; and it is invariably connected with old age. 
The cause seems to be an excess of alkaline and 
