60 A LABORATORY MANUAL OF BOTANY 
LESSON XXXII 
A comparison of the structures of plants of different 
societies 
Materials.—Stems and leaves of plants from different 
sorts of conditions, as water-lily, water-hyacinth, cat-tail 
flag, water-crowfoot, duckweed, liverworts; Easter lily, 
corn, beech, or various herbaceous plants; cactus, oleander, 
rubber-plant, century-plant; also the root of a plant from 
each society. 
If time for as many as three exercises upon this subject 
can be had, it will be very much better to divide the 
work, using plants from one of these groups for each labora- 
tory exercise. Comparisons resulting from such studies 
will be much more valuable than if all are studied in one 
lesson. 
Stems.—Compare the stems from different regions, not- 
ing relative size, solidity, and strength as supporting organs. 
Make cross-sections, study the structure, and show in 
notes and drawings how each structure is adapted to the 
way in which the plant lives. 
Leaves.—Note the relative number of leaves, their 
breadth, thickness, and strength. Can it be said that plants 
in any of these groups tend to have more leaves than the 
others ? 
Peel off and mount the epidermis from both surfaces of 
leaves of the different groups. Note where the stomata 
are placed in different plants. Which plants have most 
stomata? Would not the stomata of the water-lily be bet- 
ter protected on the other side of the leaf? Why do they 
not develop on the other side? 
Make sections of the leaves and note: 
Relative amounts of cuticle and epidermal tissue. 
Depth from the leaf surface and protection of guard- 
cells of the stomata. 
