ng 
or 
(2) The cause of the drying up of the soil by the plants is to be 
found in the very considerable transpiration of aqueous vapor by 
their leaves. 
(3) The plants deprive the soil of water in proportion as they 
stand closer together and have developed their tops more luxuriantly. 
(4) The influence of the vegetation on the moisture of the soil 
extends to the deeper layers of soil. 
(5) The moisture of the soil under a layer of inert objects, such 
as dead plants, manure, straw, pieces of wood, windfalls, etc., is 
always greater than that of the uncovered soil. 
(6) The retention of the moisture in the soil under a cover of dead 
matter is a consequence of the protection afforded by the latter against 
the influences that favor evaporation. 
(7) The quantity of moisture in the soil is, within certain limits 
and to a depth of about 5 centimeters, or 2 inches, greater in propor- 
tion as the covering of dead matter is thicker. 
(8) The soil shaded by living plants is, under otherwise similar 
conditions, driest during the growing period, but that covered by 
dead objects is the moistest, while that which is not cultivated, not 
covered with plants and naked, is midway between the two previous 
in reference to its relations to moisture. 
Wollny has also studied the influence of plants and shade upon the 
drainage of water from the soil. His conclusions are: 
(1) A notably smaller quantity of water drains through the soil 
supporting living plants from the same quantity of rainfall than 
through a naked soil during the growing season. 
(2) The quantity of drainage in cultivated fields is less in pro- 
portion as the plants stand more closely together and in proportion 
as they have developed themselves more luxuriantly. 
(3) The quantity of drain water from a soil covered by inert 
objects is increased in comparison with that from fallow land in 
proportion as the covering layer is thicker, up to a certain limit, up 
to about 5 centimeters, beyond which a further increase in the thick- 
ness of the covering steadily diminishes the quantity of drainage 
water. 
(4) For the same quantity of rain and under otherwise similar 
circumstances, the soil covered with dead leaves and similar objects 
furnishes the greatest quantity of drainage water up to a covering 
of about 5 centimeters thickness; the naked, fallow land furnishes 
the next smaller quantity of water; the soil covered with living plants 
furnishes the least quantity of drain water. 
