250 PRACTICAL BOTANY. 



b. Make similar observations on the Hop and the Honey- 

 suckle. Do the Bean, Hop, and Honeysuckle twine about 

 the stake in the same direction ? 



32. Study other autonomous movements of plants. 



a. Observe the position taken by the leaves of various 

 plants during the different hours of the day. The leaves 

 move in such a way as to present their upper surfaces in 

 such a manner as to receive a favorable amount of heat 

 and light from the sun. In cases where the full light and 

 heat would be too much for the plant, other positions are 

 taken. Observe and record some instances in which the 

 plant presents its upper surface in a position nearly per- 

 pendicular to the direction of the sun's rays through the 

 day. 



b. Place a clump of Clover plants together with consid- 

 erable earth clinging to the roots in a flower pot, or use 

 seedling Cabbages or Sunflowers. Study circumnutation 

 by Darwin's method. Insert a small stick firmly in a ver- 

 tical position, and, by means of pieces of gummed paper so 

 applied that they will not injure the plant, fasten the peti- 

 ole of a healthy leaf to the stick, leaving the blade of the 

 leaf projecting above the top of the stick. By means of 

 shellac, dissolved in alcohol, fasten a light glass thread, 

 made by drawing out a glass rod, along the midrib of the 

 leaf, and allow it to project half an inch bej^ond the tip of 

 the leaf. Place the plant where it will receive the light 

 from above. A convenient arrangement is to place the 

 plant in the bottom of a deep box painted black on the 

 inside, and reflect the light down through the open top by 

 means of a mirror. Arrange a graduated scale opposite 

 the glass index. Observe the position of the index at dif- 

 ferent hours of the day and record the results. 



33. Sleep of plants. 



a. Observe the position of the Clover, Wistaria, Wood 

 Sorrel {Oxalis acetosella), young plants of other species 



