58 A LABORATORY MANUAL OF BOTANY 
posed to the air. How do they differ in general texture? 
In breadth and number of subdivisions? Have submerged 
leaves or plants any advantages relative to temperature? 
Floating leaves and those exposed to the air usually 
have extreme exposure to the light. Do you find anything 
in their general structure indicating adaptations to this 
direct exposure? 
Note whether plants are free or attached to mud or 
soil? If attached, does the form of attachment indicate 
that it serves as an anchor merely or as a support. How 
* are the roots used in the reproduction of these plants? 
How do the floating plants obtain their supply of soil 
substances? 
Make sections of the stems of various water-plants and 
see what structures they have in common. Of what advan- 
tage are these? 
Show what you believe to be the relative advantages and 
disadvantages of submerged, floating, and erect plants. 
How do running-water societies and those of quiet water 
differ? 
Observe the plants around the pond extending back to 
“dry land.” Are the plants of the same species as those 
found in the water? Can they be divided into definite 
areas grading back to dry-land plants? If so, do the areas 
correspond to changes in moisture or other changes in the 
soil? In your notes describe in detail the different groups 
of plants observed about the pond. 
LESSON XXXI 
A rock or cliff society 
Materials.—Select a region where beds of stone crop out, 
thus forming cliffs or an essentially rock substratum. In the 
absence of a stone cliff, a steep clay slope or the slope of a 
rapidly eroding hill will afford a good region for study. 
