22 STUDY OF COMMON PLANTS. 



VII. Notice the way the different seedlings break 

 through the ground. Do those of all the dicotyledonous 

 plants behave alike? How do they compare with those 

 of Indian corn and other monocotyledons ? ^ 



VIII. Examine seedlings of squash, melon, or cucum- 

 ber, comparing specimens that are just rupturing the testa 

 with older ones. Observe the position and structure of 

 the " peg," and the way it aids in throwing off the seed- 

 coats.^ 



IX. Ascertain whether direction of growth is affected 

 by external conditions. 



1. Compare mustard or other seedlings grown in the 



dark with others growing in front of a window. 



2. Turn on their sides some of the pots with seedlings 



a few inches high, and after a day or two notice the 

 result. 



3. Observe the effect of slow change of position in neu- 



tralizing geotropism and heliotropism.^ 



X. Take up a seedling of wheat about two weeks old, 

 and examine the grain. 



1. Notice how it differs from a grain that has not 



sprouted. 



2. Remove a small portion of the endosperm and ex- 



amine under a high power of the microscope. 

 Compare the starch grains with those of wheat 

 that has not sprouted. What changes have taken 

 place ? Draw some of the grains that show " cor- 

 rosion." 



:/• 



1 Darwin, Power of Movement in Plants, p. 77 et seq. 



2 Darwin, I.e., p. 102. 

 " For this purpose an instrument known as a klinostat is employed. 



Cf. Goodale, Physiological Botany, p. 408; Sachs, Physiology of Plants, 

 p. 684. Less expensive apparatus is easily devised. 



