LEAVES WITH BEGABD TO LIGHT. 



439 



i. ii. iii. 



from the base to the apex of three leaves were +70°, +66°, +34°; 

 the plant was then placed on the klinostat in the zenith position 



at a north window. It remained in rotation till July 13, 10.30 a.m., 



i. ii. iii. 



when the leaves were at +25°, +25°, +30°, showing that apo- 

 geotropism is not needed to keep the leaves even somewhat in 

 front of the diaheliotropic plane. 



Experiments with Cherries. 



The plants used in these experiments were seedlings, having 

 woody stems about 10 centim. high ; the terminal buds developed 

 into healthy green stems, and produced vigorous leaves in the 

 course of the summer months, during which the experiments were 

 carried on. The plants were grown in earth in the above-men- 

 tioned small wooden boxes, or in small flower-pots, which could 

 easily be fitted on to the klinostat. 



Some preliminary experiments were made on the behaviour 

 of cherries growing, not on the klinostat, but in the normal posi- 

 tion, to ascertain the way in which they react to light and gravity 

 in various combinations*. 



When lighted from above, the leaves of the seedling cherry- 

 trees assume a position either a few degrees above or below the 

 horizon. The young leaves are at first highly inclined ( + 60° or 

 + 70°), and bend epinastically down in the natural course of 

 growth until they reach the horizontal position. 



Experiment 1 (Table X.). — The first experiment was made to 

 find out whether the leaves of the cherry can adapt themselves 

 to lateral illumination. A plant had two leaves opposite to each 

 other, the lamina of leaf i. being 8° above, that of leaf ii. being 70° 



below the horizon. 



Table X. 



Date. 



i. 

 Lamina. 



ii. 

 Lamina. 



May 20 



o 



+ 8 

 -40 



O 



-70 

 +53 



May 24 





It was then (May 20th) put close to a window, leaf i. pointing 



* Seedling plants of oak and horse-chestnut were also tried, but were not 

 found sufficiently sensitive to gravity or light to be useful plants for the expe- 

 riments. 



