14 



THE COCO-NUT 



CHAP. 



wetter ground. It is also true that from very dilute 

 solutions roots will absorb the dissolved salts in a pro- 

 portion greater than that in which they are present 

 in the water. The estimates which have just been 

 given are based on work at San Eamon in Mindanao, 

 on a variety which produces remarkably large nuts. 

 The number of nuts per annum on which this estimate 

 is based is too low, but the loss of mineral food in each 

 nut is greater than would be found to be the case 

 almost anywhere else in the world. 



Definite statistics, so far as they are available, on 

 the influence of outside conditions on the rate of trans- 

 piration are of great interest. It has already been 

 pointed out that the lightest haze obscuring the sun- 

 light has a marked effect in cutting down the 

 transpiration. In real shade, such as is produced by 

 heavier clouds, or by foliage between the coco-nut leaves 

 and sun, the transpiration will be cut to sometimes as 

 low as ^ of what it would be in full sunshine. How 

 great this decrease is depends, of course, on the intensity 

 and duration of the shade in question. 



The wind makes a difference in the transpiration of 

 all leaves, but makes a much greater one when the 

 leaves are in full sunshine. Thus in direct sunshine a 

 breeze estimated at five miles an hour made the trans- 

 piration four times as great as it was in still air. But 

 in the shade the wind of this velocity did not add more 

 than 50 per cent to the rate at which the leaves lost 

 water. 



Aside from the difference in transpiration due to 

 varying outside conditions, the rate at which the leaf 

 will transpire varies with its age. When the leaf has 

 just expanded, its protective structures are not as thick 

 as they afterwards become, and for several months after 

 this time there is a gradual decrease in the rate of 

 transpiration. In old leaves, on the other hand — that 

 is, in leaves from eight months after expansion up to 

 the time they fall — the rate of transpiration increases, 

 so that in leaves a year or more old it is considerably 



