PHYSIOLOGY OF THE COCO-NUT 15 



more active than it is in leaves which have just reached 

 their full size. In time of very severe drought these 

 older leaves fall off with unusual rapidity, and since 

 these older leaves are the ones which would lose most 

 water, the tree manages to cut down its loss in this 

 way to a very considerable extent. 



It is of course not to be understood that transpira- 

 tion is the only function of the leaves, nor even that 

 it is the most important work which they perform. 

 The leaves are the laboratories or kitchens in which the 

 food of the whole plant is prepared. It is in the leaves 

 and here only that starch or sugar is formed, and from 

 this starch or sugar the whole structure of the tree is 

 built up ; and from this starch and sugar, again, is 

 made all of the oil in the nuts. Light is absolutely 

 indispensable for this assimilative work in the leaves, 

 and the rate at which this work goes on is in general 

 nearly proportional to the amount of direct sunlight 

 which the leaves receive. For the sake of the plant's 

 organic food, then, even more than for the sake of its 

 mineral food, it is necessary that the coco-nut leaves 

 receive as much sunlight as can possibly be obtained. 

 A full appreciation of this fact is the necessary basis 

 of any understanding of the serious effect which an 

 improper choice of locality, or too close placing of the 

 trees in planting, or poor judgment in preventing the 

 shading of the trees at any age, will have upon the 

 success of any coco-nut plantation. 



Growth of Leaf. — During the past four years I 

 have had made by students in the Philippine College 

 of Agriculture a very extensive set of determinations 

 of the rate of growth of coco-nut leaves. The total 

 number of determinations of this kind to date is 

 between ninety and one hundred thousand. The work 

 is extended to give each student thorough first-hand 

 knowledge of the rate at which the leaves of the coco-nuts 

 may be expected to grow, of the influence of treatment, 

 weather conditions, etc., upon the rate of growth, to 

 qualify him to determine, by measurements of the rate 



