PROTECTION AGAINST HEAT, COLD, AND ANIMALS 33 
If the season or location is not favorable, some of the 
chief changes in preparation for discarding leaves can be 
illustrated in the laboratory by disturbing the roots and 
ceasing to water such potted plants as geraniums, begonias, 
and sunflowers. 
If woods and the season are convenient, several weekly 
lessons should be given to this subject, and a much more de- 
tailed outline used; while if only one lesson is given, the 
outline below must be considerably changed. 
Colors.—Observe differences in leaf color, and make 
notes upon the various colors appearing, the order in which 
they appear, and the time required in different plants for 
transition from one color to another. Do all the leaves of 
a given plant assume the same color at the same time? If 
not, what particular part of the plant precedes others? 
Does the color appear all over a single leaf at once? If not, 
is there any regular order of coloration on the different parts 
of the leaf? Do all plants of a given species show the same 
colors at one time? Does the slope of the ground upon 
which the trees stand seem to affect the color changes? Do 
the leaves of plants standing near water develop color in 
the same way and at the same time as those standing in 
drier places? Do exposed trees and those crowded together 
develop colors alike? 
Formulate a statement showing the color changes in dif- 
ferent trees and the dates on which they are observed. Do 
shrubs and herbs pass through essentially the same color 
changes as the trees? 
Leaf fall—Do leaves begin to fall when color changes 
begin ? 
See whether a leaf that has begun to change color is 
more easily removed than one that has not. Does it 
“bleed” at the point of separation? Compare with one 
that has passed through all its color changes. 
Does the slope of the ground or the nearness to water 
