IOO RELATION OF PLANTS TO TEMPERATURE 



inner segment of the flower, allowing both filaments to project 

 about three cm. beyond the flower. Set the bottle on a. stand 

 and adjust a millimeter scale horizontally so that the distance be- 

 tween the two filaments may be read off". Make the above prep- 

 arations at a temperature of 12-15 C, and after a few minutes 

 carry the preparation into a warm room at 20 C. Read the 

 distance between the points of the filaments in 5, 10, and 15 

 minutes, on a horizontal millimeter scale. 1 Replace in a cold 

 room or out of doors and note result. 



155. Thermotropic Reactions of Tendrils, Dionaea, etc. The 

 thermotropic reactions of tendrils discovered by the author, 2 and 

 exploited by Correns, 3 as well as the movements of Dionaea when 

 exposed to rapid changes in temperature, are examples in which 

 the mechanism of response, designed to make adjustments to one 

 class of forces, may be set in action by unlike agencies. 



Such reactions may be observed if a tendril of Passiflora is 

 quickly warmed eight or ten degrees by means of being thrust 

 into a hot air chamber, or if a flask full of hot water is held near 

 it. Thermotropic stimuli may be given Dionaea by thin streams 

 of water at various temperatures. 1 



^Pfeffer, W. Physiol. Untersuch. 181. 1873. 



z MacDougal. The tendrils of Passiflora coeruka. Bot. Gazette. 18 : 125. 1893. 



3 Correns, C. Zur Physiologie der Ranken. Bot. Zeitung, 54 : I. 1896. 



4 MacFarlane, J. M. Contributions to the history of Dionaea muscipula Ellis. 

 Contr. Bot. Lab. Univ. Penn. 1 : 20. 1892. 



