i PHYSIOLOGY OF THE COCO-NUT 11 



the roots cannot take up the water nor the stems 

 transmit it as fast as it evaporates under most favourable 

 conditions from the leaves. Accordingly, the sides of 

 the leaflet begin early in the day to be lowered by the 

 hinges, and the width of the leaflet from edge to edge 

 may be decreased as shown by this table : 



Leaf. 



December 7. 



7 A.M. 



8 A.M. 



9 A.M. 



10 A.M. 



11 A.M. 



12 m. 



1 P.M. 



A 

 B 



mm. 

 20-3 

 25 



mm. 

 20-3 

 25 



mm. 



17-5 

 21 



mm. 

 15 

 20 



mm. 

 13 

 18 



mm. 

 12-5 

 17 



mm. 

 12-5 

 16-5 



Leaf. 



December 7. 



December 8. 



2 P.M. 



3-30 p.m. 



5-10 p.m. 



6-30 a.m. 



7-30 a.m. 



8-30 a.m. 



A 

 B 



13 

 16 



13 

 17-5 



17 

 21-5 



20-3 

 25 



20-3 



25 



20 

 23 



Leaf. 



December 8. 



Dec. 9. 



9'30 a.m. 



10-30 A.M. 



12 M. 



1 P.M. 



2 P.M. 



4 P.M. 



5 P.M. 



6-30 a.m. 



A 

 B 



16-5 

 21 



13-5 

 18-5 



12 

 16 



13 

 16-5 



12-5 

 15 



13-5 

 17 



16-5 

 21 



20*5 

 25 



What this dropping of the sides of the leaf really 

 measures is a decrease in the amount of water in the 

 leaf below the amount necessary for the most active 

 transpiration ; in other words, it measures, the leafs 

 want of water. And what actually regulates the amount 

 which will evaporate from the leaves on days of brightest 

 sunshine and greatest dryness of the air is the amount 

 of water which can reach the leaves. At the same time, 

 this factor is by no means the only one which regulates 

 transpiration, even on such days ; for the leaf can draw 

 on the supply stored in itself and in the stems, and so 

 create a moderate deficit which will be made up during 



