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limits, the fewer the trees the better they can develop and the 

 greater is the tendency to produce short, thick trees ; but the sup- 

 plying of areas of soil beyond the reach of the best developed 

 roots during the first ten years' growth will not necessarily be 

 accompanied by a much increased rate of growth during that time ; 

 there appears to be an average incremental rate of growth for 

 parts of plants, often of specific importance, and beyond which 

 it is often undesirable or impossible to go. Trees which are 

 widely planted do not appear to reach the tappable size — 20 to 24 

 inches at a yard from the ground--much quicker than those 

 planted ten or twelve feet apart : subsequently the wider planted 

 trees increase in circumference quicker than the closely-planted 

 ones, other conditions being the same. 



YIELD PER TREE AND PER ACRE. 



The better developed the tree the larger is the yield of rubber 

 obtainable and the better able is the plant to stand the effect of 

 tapping operations. 



The differences in yield obtainable from an acre of 100 trees 

 planted 20 x 20 feet and one of IQO planted 15' x 15', or 430 

 planted 10' x 10' have not yet been demonstrated ; closely planted 

 areas during the first few years would probably give more rubber 

 acre for acre, than those widely planted, but as time went on the 

 average yield, per tree, would increase on the widely planted area 

 with the more continuous increase in circumference. 



The differences in total yield per acre, of 430, IQO, and 100 trees 

 in the 1 2th or 20th year are not known, but there are reasons for 

 imagining that the intermediate number would give satisfactory 

 results at such periods ; if the total yield per acre, is, as has been 

 stated, approximately the same, no matter what the differences in 

 distance is, it means that if the widely planted trees give each 

 2 lb., of rubber each, per year, those on the other estates must give 

 approximately I and 0*46 lb. respectively. 



It is generally believed that the great advantage of permanent 

 wide planting over permanent close-planting lies in the check given 

 to the spread of diseases and the better control which the planter 

 has over them. This is, however, in a great measure only tempo- 

 rary, for, once the roots have met and the branches come into 

 contact, the conditions are more nearly equalised. It may even be 

 disputed whether the differences in distance between widely and 

 closely planted trees of Para rubber is an effective check against 

 the spread of many diseases, especially where leaf pests are con- 

 cerned. Distance does not give immunity from attack on an ordi- 

 nary rubber estate ; the differences under discussion are trivial 

 when one considers how spores and insect pests may travel. 



STERILIZATION OF SOIL. 



No one who has worked with the Ceylon soils will dispute the 

 fact that exposure of the surface soil to the sun and rain, for a 

 period of several years, results in a great loss. The soluble con- 

 stituents are carried away in the drainage water, the organic 

 matter is reduced in quantity, the ground becomes hard and caked 

 and the destruction of useful bacteria assured. The loss occa- 



