50 EXPERIMENTAL PLANT PHYSIOLOGY. 



The roots will point outward and downward, and the shoots 

 upward and inward. These positions will be taken by rapidly- 

 growing seedlings in 5 or 6 hours. 



EXPERIMENT 68. 



REPLACEMENT OF GRAVITY BY CENTRIFUGAL FORCE. 



If a water system is at hand, the rapid rotation of the wheel or disk 

 holding seedlings may be accomplished by the following apparatus 



FIG. 51. 



Centrifugal apparatus. (After Oels.) A, heavy board base ; B, cork hold- 

 ing the sealed end of a glass tube which serves as a bearing for the end 

 of the axis of the wheel. 



and the seedlings may be kept moist during the experiment. Upon a 

 wire, 40 centimeters long, the size of a knitting-needle, are strung at 

 equal distances a number of circular cork plates, 3 cm. in diameter 

 and a half-centimeter thick. The wire is now bent in the form of a 



