14 BULLETIN 521, U. S. DEPARTMENT OF AGRICULTURE. 
rise of capillary water depend ? Of what practical importance is the 
relation of capillary water in soils to the farmer? How will it affect 
his management of soils of different types? 
Note. — As a preliminary to this exercise capillarity may be demonstrated to 
the class by dipping a cube of sugar in water colored with ink. 
Exercise 11. — Use of Water oy Plants. 
Purpose: To show how plants giye off moisture and to giye an 
idea of the amount of water used by plants. 
Directions: Start a pea yine or some other plant which will grow 
vigorousb T in a flower pot. After the plant is growing well coyer 
the top of the pot with a piece of cardboard somewhat larger than 
the top of the pot. cutting a slit in the board for the plant. Seal the 
slit with pitch, wax, or tallow so that no moisture can evaporate from 
the soil. Coyer the plant with a glass jar and set in a warm, sunny 
place. If the jar is cooled by wrapping it for a minute or two in 
a cloth wrung out of cold water, moisture will condense on the inner 
surface of the glass. 
To determine the quantity of water used, the same plant may be 
used if there is a space to hold water between the surface of the soil 
and the cardboard. "Water should be applied as needed, lifting the 
cardboard to apply it. Weigh all water given, keeping up the test 
for a month or as much longer as conyenient. At the end of the test 
dry the plant thoroughly, weigh it. and then determine the relation 
between the dry matter and the water needed to produce it, 
Record and repoi^t: Each student should make a record of the 
water used and make a written report of results in which he should 
answer the following questions: Where does the water on the glass 
come from ? How is this water giyen off by plants ? Is all water ab- 
sorbed by the roots giyen off by the leayes ? What is the f unction of 
water in the plant? About how much water is used to make a pound 
of dry matter in the plant tested ? How does this test agree with pub- 
lished reports? 
Exercise 12. — Effect of Mulching on Conservation of Moisture. 
Purpose: To test the efficiency of different mulches. 
Directions: Six cans or pots of equal size should be filled with 
equal quantities of loam soil of uniform grade. Fill within 2 inches 
of the top and wet thoroughly with equal quantities of water. These 
cans should then be treated with mulching material as follows: (1) 
Left as a check, (2) coyer with 1J inches of soil and pack it down, 
(3) coyer with the same amount of the same kind of soil, but keep 
it loose by stirring from time to time. (4) coyer with 1§ inches of 
grayel, (5) coyer with H inches of fine road dust, and (6) coyer with 
1J inches of chaff, sawdust, or bits of dry leayes. Keep all cans under 
similar conditions. Weigh morning and evening for five days. 
