COCONUT PLANTER'S MANUAL. 13 



replaced by fresh growths from the living parts of the same roots. 

 The direction of the primary roots is mainly horizontal. Some may 

 go down to a depth of about three feet or so, but most are found at 

 depths varying from 6 to 1 8 inches, according to the nature of the 

 soil. 



Roots will not grow any depth into water or a water- logged soil, 

 while they cannot thrive in a very dry one : hence their tendency to 

 grow downwards in a sandy soil. The best conditions for growth 

 are a deep soil, with a deep water table, and the surface soil not 

 allowed to become too dry. Surface cultivation is, therefore, to be 

 commended, but not deep enough to destroy too many roots. 



The tip of the root will be found to terminate in a tough 

 structure called the root-cap, which serves to protect the growing 

 point from injury. Just behind this is a region made up of a delicate 

 structure, generally light in colour, through which water and soluble 

 plant food are absorbed, for the coconut has no root-hairs like 

 dicotyledons such as the mango and jak. When root growth is 

 checked by drought this region almost disappears by encroachment of 

 the tough external coat which invests the rest of the root. 



On old coconut roots are often seen numerous, small, white 

 root-like structures which are specialized roots adapted for breathing 

 purposes. These breathing organs allow air f o pass into the 

 internal tissues of old roots which would otherwise die for want of air. 



If a root be cut through, the end is promptly sealed up by a 

 gummy substance, and no absorption takes place through it. The roots 

 of the coconut freely absorb strong solutions of common salt without 

 injury. The ordinary process of absorption is carried on most rapidly 

 in the forenoon, less so in the afternoon, and very slowly at night. 

 The tree does not appear to store up any great quantity of water, 

 which passes freely out through the leaves. Anything, therefore, 

 which interferes with evaporation from the leaves, will check absorption 

 thi'ough the roots. 



The finer roots appeal- to take up more water than the large 

 ones. A calculation based only on the activity of the main roots 

 showed that a tree takes up about six gallons a day ; but, by a determi- 

 nation of the evaporation from the leaves, this must be far below the 

 actual figure. Investigations have shown that the average growth of 

 roots is rather more than three feet per annum, 



