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26 MANURING THE SOIL. _ 
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* criminating between what is good for them, and what will be inyuri- 
ous. The spongioles thus imbibe urated liquid ; ‘and, loaded 
with this improper food, the I a an corzed snake, 
become distended, the fine epidermis that covers them is torn asunder, 
* » their power of capillary attraction is gone, and they can neither for 
the food they have taken up, into the main roots, nor reject the aan 
‘» _ mentitious matter sent down to them from the leaves, after the elabo- 
ration of the sap. . In this state of things, from the usual circulation 
of the fluids being impeded, it is not surprising that the plant should 
droop, that its leaves should turn yellow, that its flowers should not 
. expand, that its fruit should shrivel and drop off prematurely, and 
that in the end it should die; as, in fact, it may be said to expire of 
apoplexy, brought on by indigestion. 
All soil, to be in a fit state for growing plants, should be suffi- 
ciently loose and dry to allow of passing through it intermixed with 
air; as water, when in this state, is never more than slightly impreg- 
nated with the nutritious juices of the manure through which it has 
passed. The spongioles are thus not supplied with more food at a 
time than they can properly take up and digest, and a healthy circu- 
lation of the fluids is kept up through the whole plant. But, what, 
it may be asked, is to be done with a garden, the soil of which has 
become black and slimy hike half-rotten peat? The quickest remedy 
is covering it with lime, as that combines readily with the humic 
acid, and reduces it to a state of comparative dryness: or, if sub- 
soil be good, the ground may be trenched, and the surface-soil buried 
two spits deep ; but in both cases it will be necessary thoroughly to 
drain the garden to prevent a recurrence of the evil. 
All the different kinds of soil found on level nd, consist of two 
parts, which are called the surface-soil and the sub-soil ; and as the 
sub-soil always consists of one of the three primitive earths, so do 
these earths always enter, more or less, into the composition of every 
sind of surface-soil. The primitive earths are—silex, (which includes 
sand and gravel,) clay, and lime, which includes also chalk; and 
most sub-soils consist of a solid bed or rock of one or other of these 
materials, probably in nearly the same state as it was left by the 
deluge. The surface-soils, on the contrary, are of comparatively 
recent date; and they have been slowly formed by the gradual 
crumbling of the sub-soil, and its intermixture with decayed animal 
and vegetable matter, and with other soils which may have : 
had 
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