PLANTS AND THE LIGHT 25 
Change the position of the dish containing water-plants, and 
see whether they readjust themselves. Will these plants 
turn, as often as they are changed in their position, for light 
exposure ? 
Examine the locust, pea, or clover, the wild lettuce, and 
compass-plants in early morning, noon, and late afternoon, 
and see whether the leaves change position. At each exami- 
nation note from what direction the light is striking the 
leaf. In the wild lettuce, compass-plant, and clover note 
especially the leaf positions at noon on a very hot day. 
Which leaves change their positions during the day? Try 
to find some of these plants growing in shaded places and 
see whether their leaves have colors and positions similar 
to those that are growing in open places. Is the arrange- 
ment of the leaves in the shaded and open regions more 
alike at night or in the day? Do the exposed plants have 
the same leaf positions on cloudy as on bright days? How 
do you account for the various positions found? Do the 
leaves of young and old plants behave in the same way in 
reference to these points? 
At midday place some oxalis plants in a dark closet 
and see what leaf changes occur. To what cause do you at- 
tribute these changes? Place in the light again and observe. 
Observe plants, such as corn and other grasses, which 
fold their leaves during very hot dry days. In what ways 
may this position be of advantage? 
