22 
LABORATORY EXERCISES 
III. The membranes of plant cells are semipermeable. (See 
Waggoner, Page 104.) They prevent the concentrated contents 
from passing outward and thus are largely responsible for the 
condition known as turgor. (See Waggoner, Page 104.) Wash a 
slice of fresh red beet in cold water. What is the color of the water 
following this process? Has the beet lost any of its firmness? 
Place the beet in water and heat it. What do you now observe 
with regard to the color of the water? Does the character of the 
beet change? If so, how? What has been the effect of the heat 
upon the character of the protoplasmic membrane within the cell 
walls? 
EXERCISE 24 
SOILS 
I. Field Study. Provide yourselves with a trowel and a few 
dishes or large-mouthed bottles. 
1. Visit some small stream which flows down a gradually 
decreasing slope into a pool. Observe the arrangement of the soil 
particles which have been deposited after being carried by the 
water of the stream. As the current slackens, which particles, 
with relation to size, have been dropped first? Which last? Why? 
Do you find any sediment still clouding the water of the pool? 
That is, is it still muddy ”? Take this water to the laboratory 
for further study. 
2. Examine some blue grass sod. What is the relation of the 
roots to the soil? What causes the formation of sod What 
does the decay of the dead grass roots have to do with the addition 
of organic matter to the soil? By what other means may organic 
matter be added to the surface soil? Take a sample of soil con¬ 
taining organic matter. 
II. Laboratory Study. Study each sample of soil which the 
instructor has mounted under the low power of a microscope. 
Make a drawing of particles of each sample. From your observa¬ 
tions, discuss the composition of soil. 
