Jan. 1907.] 



8 



Saps and Exudations. 



The advantages of close planting are that there is a larger number of trees 

 on a given acreage ; (2) the ground is better protected with the root and foliar 

 systems, and consequently expenses in weeding are greatly checked, and soil loss 

 thereby reduced ; (3) the rubber can be harvested cheaper ; (4) the cultivation is 

 essentially one of rubber trees which presumably have a higher value than other 

 trees of economic importance, and the method of cultivation over all the soil 

 becomes the same ; (5) the inevitable proportion of poorly developed, stunted, and 

 damaged trees is not as serious ; (6) it is easier to thin out a densely planted estate 

 than to interplant a widely planted one- 



The disadvantages are (1) there may be considerable interference in the 

 development of all parts of the plant and the resultant trees be dwarfed and lacking 

 in vitality ; (2) the stems will tend to become thin, long, and spindly, and the thickness 

 of tappable cortex (bark) reduced ; (3) diseases are given a greater certainty of 

 originating and may spread more rapidly because the parts of the plant are nearer 

 to one another or in more frequent contact. 



Distance according to Size and Age. 



The cultivation of trees of Hevea bvasiliensis ranks as unique in so far as it 

 has to deal with a species which grows into a tree of enormous size ; the past and 

 most of the present products, in Ceylon, cannot be compared with the latest arrival, 

 for it overtops the tallest cacao and cinchona trees, and often equals the coconut 

 palms, in height and frequently in breadth, age for age. 



* Trees less than thirty years old, which have never really been cultivated, 



have a height of 80 to 90 feet and a circumference of 80 to 109 inches ; specimens 

 planted 25 to 30 feet apart have been known to overlap their branches in about 20 

 years, and fifty years old trees in tropical America even exceed these huge dimensions- 

 This is the outstanding diffeience between the cultivation of Para rubber trees and 

 all other plants in Ceylon, and though it has been an easy matter, in the past, to 

 settle the distance at which tea, cacao, cinchona, etc., should be planted, we are now 

 confronted with a new set of conditions which may require different methods of 

 cultivation. 



Distance of Tapped Trees. 



There is another point which appears to have been overlooked in connection 

 with this subject, and that is the retardation in growth which must follow regular 

 paring or tapping. It is no exaggeration to say that most of the old trees in Ceylon 

 were not systematically tapped until the last few years, and but few estates 

 can point to acreages which have been regularly tapped, throughout successive 

 years, from the time the old trees attained their minimum tappable size. When- 

 ever cortical tissues are removed or mutilated, the energy of the plant is partly 

 diverted to the production of new tissues in the affected area, for the time being 

 the intimate connection between individual vital structures and that of the 

 latter with cells which have less important functions, is interrupted ; such changes 

 must effect the future development of the plants, especially when of repeated 

 occurrence from the 4th, 5th or 6th year onwards. In the absence of any measur- 

 able effects following the tapping of trees, one can only generalise and state that 

 the sizes of trees so treated will probably be less than those of specimens which 

 have never had their bark so excised and otherwise mutilated. Time will certainly 

 prove the wisdom or error of planting Para rubber trees ten to fifteen feet apart, 

 as most estates in Ceylon appear to be so planted. Systematic paring away of 

 the bark of rubber trees will as assuredly change the habit and ultimate dimensions 

 of the mature trees, as has the constant plucking of the leaves of tea plants, and 

 the peeling of the cinchona bark. 



