PHYSIOLOGY OF THE COCO-NUT 17 



this time, but on this point there are no observations. 

 There are likewise no determinations of the rate of 

 growth of the leaves of very old trees, but there is no 

 doubt that such leaves grow more slowly. On shallow 

 and therefore dry soil, the growth is constantly less 

 rapid than where the soil is deeper and moister. 

 We have patches of trees in which the average rate 

 of growth is not more than 25 millimetres a day. 

 Such trees come into bearing several years later than 

 do trees 50 metres away on lower and deeper ground. 



There is a natural and very evident relation between 

 the rate of growth of the leaves and the amount of 

 production of fruit. The rate of growth can be deter- 

 mined for most purposes within a few days so as to 

 get an average for groves of considerable size. To get 

 positive and reliable information as to the rate of 

 production requires observations extending over many 

 months. The easiest way in which one can secure 

 reliable information as to the condition of a grove is 

 therefore by determination of the rate of growth. This 

 can be done in several different ways. The method 

 which has proved most satisfactory is by drawing 

 marks with Indian ink across the bases of the youngest 

 and next youngest leaf, making one mark, half of which 

 is on each leaf The difference in height of the two 

 halves of this mark, after one day or one week, shows 

 the difference in rate of growth of the two leaves. A 

 similar mark is placed on the base of the next to the 

 youngest leaf, called No. 2, and the third youngest, 

 called No. 3. The break in this mark after a day or 

 a week shows the difference in growth between these 

 two leaves. Similarly, the difference between the 

 growth of leaf No. 3 and leaf No. 4, of leaf No. 4 

 and leaf No. 5, and of leaf No. 5 and leaf No. 6, are 

 determined. The lowest mark, which remains unbroken, 

 will be on the two youngest leaves which have ceased 

 to grow. The sum of the observed breaks in the marks 

 is the growth of the youngest leaf for the period in 

 question. 



c 



