xi, c, 6 Copeland: Growth Phenomena of Dioscorea 



239 



Dioscorea hirsuta No. 331, of which 6a, 66, 9, and 10 had the 

 tubers in ice water, while the remaining plants were not so 

 treated. The second horizontal line of growth figures shows the 

 growth from May 26 at 5 o'clock in the afternoon to May 28 at 

 10 o'clock in the morning at which hour the ice water was 

 applied. The remaining figures indicate the growth in milli- 

 meters during the preceding time-interval. 



Table VIII. — Effect of cold on tubers of Dioscorea hirsuta No. SSI. 



[Measurements are recorded in centimeters.] 





Growth of stem. Tuber No.— 



2a 



26 



3 



4a 



4b 



6 



6a» 



66» 



6c 



7 



8 



»» 



10 • 



Length of shoot. May 28 — 



47 



34 



92 



12ft 6 



82.3 



87.1 



71.9 



68.8 



28.9 



40.6 



64.9 



70.2 



60 



Growth, from May 26 at 5 





























p. m. to May 28 at 10 





























a.m.-. 



14 



12 o 



25 6 



17.2 



14 7 



27 9 



16 4 



15.2 



3 5 



18 8 



23 8 



28 1 



12.6 



Additional growth: 





























May 28, at 11. 40 a. m~ 



1.0 



0.7 J 1.6 



1.1 



1.0 



0.8 



0.6 



0.4 



0.1 



0.9 



1.8 



1.0 



0.3 



May 28, at 1.40 p. m — 



1.2 



1.0 1.4 



0.7 



0.9 



1.4 



0.6 



0.5 



0.4 



1.3 



1.2 



0.6 



0.3 



May 28, at 3. 40 p. m .. 



1.1 



1.0 



1.4 



0.7 



1.0 



1.0 



0. 4 I 0. 4 



0.1 



1.0 



1.4 



0.6 



0.3 



May 28, at 5. 40 p. m .. 



1.1 



0.9 



1.4 



0.6 



0.6 



1.1 



0.2 



0.0 



0.2 



1.1 



1.1 



0.3 



0.0 



May 28, at 7. 40 p. m .. 



0.9 



0.9 



1.0 



0.3 



0.6 



1.0 



0.2 



0.1 



0.2 



0.8 



1.1 



0.2 



0.1 



May 29, at 7.40 a. m... 



4.8 



3.2 



3.3 



2.0 



2.6 



6.6 



0.2 



0.3 



0.0 



5.3 



4.6 



0.4 



(") 



May 30, at 7. 40 a. m... 



14.3 



11.1 



16.1 



9.7 



10.2 



16.2 



0.4 



0.6 



0.1 





13.9 



0.6 





May 31, at 6 p. m 



22.6 



18.7 



24.1 



18.3 



16.8 



21.3 



6.0 



8.4 



0.3 







25.0 



6.9 







June 6, at 11 a. m 



70.4 



80.7 



83.4 



62.9 



40.2 



48.9 



54.1 



79.9 



28.1 





81.2 



62.0 





Tubers in ice water. 



b Injured. 



As Table VIII shows, the effect of chilling the food store was 

 shown with considerable promptness in the rate of growth, even 

 when the growth was occurring at a distance of more than 1 

 meter. The figures near the bottom of the table show that, 

 after the food stores were permitted to become warm, there was 

 a prolonged after-effect of the chilling. However, this cannot 

 have been due to any permanent injury, such as killing the food 

 stores or many of their cells, for the ultimate growth was at 

 about the same rate in all of the plants; and it occurred at 

 about the same rate, whether or not the roots were immersed 

 in water. 



To test the effect of cold upon the rate of translocation, double 

 glass tubes, 20 centimeters in length, were prepared, the inner 

 tube containing the stem and being so small that the stem nearly 

 filled it, and the outer tube carrying a stream of water which ran 

 from a can containing ice. As I set the experiment up, it was 

 impossible to lower to below 8° the temperature of the water 

 leaving the outer tube. The temperature in the inner tube was 



143573- 



