I 



Jan. 1907. J ? Saps anrl Exudations. 



moment can doubt that, within limit?, the fewer the trees the better they can 

 develop and the greater is the tendency to produce short, thick trees ; but the 

 supplying 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 

 undersirable 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 190 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, 190, and 100 trees in the 12th 

 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 

 1 and 0"46 lb. respectivelv. 



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

 contact, the conditions are more nearly equalised. It may evenbe disputed whether 

 the differenses in distance betweeu widely and closely planted trees of Para rubber 

 is an effective check against the spread of many diseases, especially where leaf pests 

 are concerned. Distance does not give immunity from attack on an ordinary 

 rubber estate ; the differences under discussion are trivial when one considers how 

 spores and insect pests may travel. 



Sterilisation 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 constituents 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 occasioned in tea 

 clearings, where the plants are planted three to four feet apart, or on cacao estates 

 where cacao saplings, distanced nine to twelve feet apart, are interplanted with 

 Erythrmas and Albizzias, has been considerable ; but in the wide planting of rubber 

 trees alone, a much larger proportion of the soil is exposed for many more years, and 

 the loss of food constituents and sterilisation of the soil become much more serious 

 matters. This constitutes a very serious disadvantage against permanent wide 

 planting of Para rubber trees. The reduction in available tapping area consequent 

 on the fewer number of trees on widely planted estates is an objection of 

 importance in the early tapping years, and the fewness of the trees would ensure 

 that the death of a single tree would be occasioned with relatively more 

 serious loss. 



