FOR WAGGONER’S BIOLOGY 
29 
EXERCISE 31 
THE INTERNAL STRUCTURE OF A LEAF 
Study prepared cross sections of leaves under a hand lens or the 
low power of a microscope. (If these are not available, study the 
diagram in the text. See Waggoner, Page 145.) 
I. Note the dark-covered oval areas which are scattered through 
the section, and determine the relation of these to the fibrovascular 
bundles of the petioles and veins. Of what are these bundles com¬ 
posed? Next note the upper and lower layers of cells. These 
constitute the epidermis. The outer walls of the epidermal cells 
are covered with cuticle. Below the epidermis note the layers of 
thin-walled, elongated cells which are closely joined together. 
This is the palisade tissue. Note the chloroplasts, the numerous 
green bodies in these cells. Below the palisade tissue note the 
region of thin-walled cells and numerous air spaces. This is the 
spongy tissue. In the lower epidermis note the stomates. 
II. Make a drawing of the cross section, labeling each of the 
structures shown. 
EXERCISE 32 
PHOTOSYNTHESIS 
1. 1. Place a green water plant (green alga or “ water moss ”) 
in a jar or beaker of water. Fill a test tube with water and invert 
the test tube and a funnel over the plant. (See Waggoner, Fig. 86.) - 
Into what does any gas pass which arises from the plant? Place 
the apparatus in the sunlight and observe. Note the bubbles 
which appear. From what do they come? Now shade the plant 
and observe any changes which occur. 
2. Place the plant in the light and leave it for several hours. 
Then test the gas in the test tube for carbon dioxide and for oxygen. 
(See Appendix.) Use the lime water test first. Why? Which 
is present, carbon dioxide or oxygen? What is its origin? Where 
did the chemical elements come from which were used in the process 
of photosynthesis? 
