GROWTH OF SEEDLINGS 77 



After a day or two observe the plant and discover what 

 the positions of stem and root are with reference to the light. 

 How does the stem differ from the root as to its direction of 

 growth ? 



Conclusion. State the result and 'the probable cause. 



65. GROWTH 



Object. To find out what happens if a plant meets 

 with an obstacle in the path of its growth. 



Method. Place bits of stone, wood, etc., where they will 

 interfere with the growth of (a) roots and (6) stems. 



Suggestion. This can be easily done by placing the 

 seedlings on damp blotting paper covered with plate glass. 

 The obstacle and the plant can thus be plainly seen at all 

 times. 



Note. See also Experiments 158, 159, 160, 161, on plant move- 

 ments due to contact. 



66. GROWTH 

 Object. To study the rapidity of growth. 



Apparatus. The auxanometer is an apparatus designed 

 to show the rapidity of growth of a plant. 



A simple form of this device is shown in Figure 24. It 

 consists of an upright fastened to a block for support. At 

 the top an arm extends in a horizontal direction and to it 

 is attached a quadrant which may be cut from white card- 

 board and marked off into ten or fifteen equal parts. At the 

 center of the quadrant is a pulley which may be made of a 

 cork centered on a stout pin about which it can freely re- 

 volve. 



