122 



Elementary Plant Physic 



133. Movements in response to a combination of 

 geotropism and phototropism Force into bloom a 

 number of bulbs of Narcissus, which may be obtained from 

 dealers. Set one upright on a table, and cover with a card- 

 board box with an opening in one side, at the level of the 

 opening flowers. Note the position taken by the flowers. 



The pedicels will be found 

 to move to a horizontal 

 position, with the axis of 

 the flower directed toward 

 the source of light. 



Take a second plant, 

 in which the flowers have 

 already assumed the hori- 

 zontal position, and lay 

 the plant inclined or hori- 

 zontally, fastening the 

 scapes in such manner that 

 the pedicels lie in various 

 planes. Note the exact 

 positions of half a dozen 

 flowers. Examine a day 

 later, and describe the 

 movements entailed. 



134. Hydrotropism 

 of roots. Secure a small 

 wooden box which will hold sufficient moist sawdust to ger- 

 minate seedlings of peas or beans. Take away the top and 

 bottom, and replace with wire or cloth gauze. Fill the box 

 with sawdust thoroughly saturated in water, and imbed seed- 

 lings in the sawdust. Attach cords to the box in such man- 

 ner that it may be suspended from a support, or provide 

 means of tilting it at an angle of 45 degrees. The box must 

 be so shallow that the roots in the natural course of growth 



Fig. 94. Box with perforated bottom, 

 filled with sawdust, to demonstrate hydro- 

 tropic reaction of roots. After Detmer. 



