Gums, Resins, 4 



the plant, and such as to allow one to collect the latex with ease and to successfully 

 operate against diseases when they arise. Generally speaking, close planting is 

 associated with interference of root growth, production of tall trees, and with the 

 rapid spread of disease ; to counterbalance these, we have the protection against 

 exposure and wash, and an increased tapping area. Now let us take each of these 

 questions and see what understanding we can arrive at. 



ROOT GROWTH. 



We all know how rapidly the superficial roots of Para rubber trees grow, and 

 what a compact mass they form when mature. The lateral roots grow at varying 

 rates according to the conditions prevailing, but if grown on moderately good land, 

 an incremental yearly increase in radius of about 10 to 12 inches may be allowed 

 for. In some districts where the soil and climatic conditions are very favourable, 

 the root growth is more rapid than this, and in others, particularly at high eleva- 

 tions, the growth is not as fast. If such a rate obtains for your estates, it means 

 that it will take five years for the roots of trees planted ten feet apart to completely 

 ramify the whole of the soil, and a proportionately longer period if the trees are 

 more widely planted. If the trees are distanced more than ten feet from one 

 another, there is ample soil in the middle of the lines for the roots of shade trees 

 green manures or catch crops, during the first few years— though ultimately these 

 should be uprooted and only the rubber roots allowed to remain in possession of the 

 soil. If, therefore, you are prepared to tap some of your trees to death at the end of 

 the fourth or fifth year, there is no very serious objection to originally planting the 

 trees ten feet apart, as far as root development is concerned. 



DEVELOPMENT OF FOLIAGE. 



Naturally one must also consider the rate of development of the foliage as 

 well as the roots. The lateral spread of the foliage depends upon whether the tree 

 is allowed to form a straight stem, as it will do if left alone, or whether it is made 

 to fork and to develop lateral branches instead. Under normal conditions one may 

 expect that the lateral branches of trees planted ten feet apart will have met by 

 the end of the fifth year, and if pruning has been carried out there is generally a 

 considerable overlapping of the foliage from adjacent trees, and the soil is partly 

 covered by tliat time. The advantages of quickly covering the soil in the tropics 

 are only too well-known and the protection of the soil by any means should be 

 seriously considered. The disadvantages of overlapping foliage are that disease 

 might spread more rapidly and that the functions of the leaves may be impaired. 

 As far as the theory of the interference of foliar functions is concerned, I think it 

 can be dismissed. The leaves are the organs wherein the food of the tree is 

 manufactured ; and in order to accomplish this they must, of course, have some 

 light. But it is a very disputed question as to whether the leaves of Para Rubber 

 require all the light which they can get in the tropics, and we all know the 

 beneficial results obtained by growing other plants under shade in Ceylon. The 

 overlapping of foliage consequent on close planting constitutes a self-shade and 

 from considerations regarding the increase in the flow of latex when light is less 

 intense, we may yet find that a moderate amount of overlapping of foliage may be 

 very beneficial for Para Rubber. From the results of experiments, I am convinced 

 that many plants, even in Europe where the light is never intense, do not require 

 constant strong light, but are able to carry on their work when supplied with 

 light intermittently. Intermittent light has been as effective as continuous light, 

 with certain plants, and from these considerations and remembering that light 

 often retards growth, I do not apprehend much interference in the functions of 

 the leaves of Para Rubber trees by a moderate amount of overlapping. 



