24 BOTANICAL GAZETTE [JANUARY 
fact that in well-washed soils even the less soluble constituents are 
apt to be actually dissolved and washed out to a greater or less degree. 
Thus, phosphates and sulfates are less abundant in well-washed 
soils than in those less thoroughly washed. 
In this glaciated region, fine soils, such as clay, were either devaada 
under the ice of the glacial epoch, and hence not well washed, or else 
they were deposited from deep and very slowly flowing water. The 
former variety usually contains many coarser particles, as loam, sand, 
and pebbles. In the case of loamy soils a good part of the fine material 
has been washed out, but a considerable amount remains with the 
sand, so as to give it its loamy character; this is especially true of the 
ridges. Sandy soils are still more thoroughly washed; the gravel 
was left farther up stream, on the sides of the ridges usually, while 
the clay was held in suspension to be deposited at a lower level, where 
the velocity decreased. 
On account of the difference in size of particles, which results 
from water washing, there naturally follows a corresponding differ- 
ence in the size of the interstitial spaces of the soil; the finer the 
component particles, the smaller must be the spaces between them. 
And because of this there comes to be a corresponding difference in” — 
water-holding power and water-lifting power. The surface tension _ 
of water films is greater and hence more effective over small surfaces _ 
than over large ones, and the film surfaces are greater in coarse than - 
in fine soil. Thus, the smaller the particles of any soil the more water — 
it can hold and the higher it can lift this liquid from a lower level. © 
WaRMING; quotes WOLLNY as having shown that quartz sand con- | 
sisting of grains over 1 to 2™™ in diameter can hold only one-tenth — 
as much water as that with grains o.o1 to 0.07™™ in diameter. | 
SCHIMPER‘ states that loose sand has a water capacity of 15.7 per | 
cent. of its volume, while clay exhibits this property to the extent of | 
49.9 per cent. 
The nature of the soil particles themselves often plays an important 4 
aia in ae the water-retaining and water-lifting power. : 
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Dr. as Roctinech. Bearbeitet von P. Graebner. 
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