24. A LABORATORY MANUAL OF BOTANY. 
Color.—Group the leaves of plants of the same species 
from the different regions, having some leaves that show 
the lower and some the upper surface. Note and describe 
color variations. 
Size, form, and number.—Observe whether plants of the 
same species from the two regions have leaves alike in size 
and form. Note the relative number of leaves in the two 
regions. Illustrate by sketches. 
Structure.—Examine leaves from the two regions as to 
their thickness, strength, and prominence of veins. Do you 
find hairy outgrowths from the epidermis? Of what advan- 
tage could hairs be in protecting leaves against excessive 
lighting? 
In the laboratory make sections of the leaves, and under 
the microscope compare (a) thickness of cuticle and epi- 
dermal walls, and (6) the amount and arrangement of chlo- 
rophyll-bearing tissue and nearness of plastids to the sur- 
face. Show differences by drawings. In notes show how 
each leaf structure is of peculiar advantage to plants in the 
region in which the structure is developed. 
LESSON IX 
Leaves and the light—leaf movements 
Materials.—In the laboratory, such plants as geranium, 
begonia, coleus, some water-plants which are growing from 
the bottom of a dish of water, as water-milfoil and Vauche- 
ria; out of doors, compass-plants, wild lettuce, locust, pea, 
clover, and oxalis. If a greenhouse is convenient, an ex- 
amination of it will afford some good class work. 
Observation and study.—Note the house plants to see 
whether they are making any attempt to get to the light. 
Do all the house plants observed behave in the same way? 
Change the position of a geranium, coleus, or begonia, and 
see how many hours or days are required for readjustment. 
