12 



THE COCO-NUT 



CHAP. 



the night while transpiration is most inactive. And the 

 greater this deficit the more water the roots will take 

 up during the night. 



As the afternoon advances, the transpiration decreases, 

 and late in the afternoon falls to the point where water 

 does not evaporate as fast as it comes to the leaves, and 

 the leaflets begin to widen ; so that the width by dark 

 is about as great as it was in the morning, which 

 indicates that the leaf has made up whatever shortage 

 of water it underwent during the day. 



By a rather complicated series of measurements the 

 following determinations were made, showing the amount 

 of water which evaporates in grams from one leaflet 

 during the hours of one day. 



Hour ending at Grams. 



7- 30 a.m. . . . 0-03 



8- 30 „ 0-14 



9- 30 „ 0-10 



10- 30 „ 0-23 



11- 30 „ . . . 0-96 



12- 30 p.m. . . . 0-81 



1- 30 „ 3-02 



2- 30 „ 1-19 



3- 30 . . . 1-78 



4- 30 „ 1-53 



5- 30 „ 0-91 

 Night .... 0-10 



Total . 10-81 1 

 1 For one pinna and one day. 



The total water evaporated from this leaflet during 

 the day was 10 '8 grams. If we allow 150 leaflets to 

 the leaf and 25 leaves to a tree, the calculated 

 transpiration for the whole tree will be 40,500 grams, 

 or 40*5 litres. Estimates based on observations made 

 in this way range from 28 to 45 litres. In this case, 

 the leaflets whose transpiration was being measured 

 took their turns in the shade and in the sunshine, as 

 the shade of other leaves fell upon them during the 

 day ; that is, they were under practically natural con- 



