PLANTING DISTANCES 119 



All will agree that a strong, deep-reaching tap-root is a most 

 desirable thing for a tree to possess, but the lateral roots 

 have a totally different function to perform. They have to 

 receive and forward to the foliage the nitrogen and ammonia 

 supplied through the agency of bacteria, and mineral salts, and 

 the deeper into the soil the roots force their way the fewer are 

 the bacteria, unless the soil is well drained, well broken up and 

 well aerated, as the bacteria must breathe. If the sub-soil 

 can be made habitable for the roots, then fresh and abundant 

 stores of mineral salts (but seldom of organic remains) can be 

 drawn upon and additional roots will be developed to draw 

 upon them, to the very great benefit of the tree. 



Take an instance in point out of many which could be cited. 

 On Pangkattan Estate, in the Bila district of Sumatra, belonging 

 to the Sumatra Para Company, there are three isolated trees 

 which, from special circumstances, have enjoyed all the ad- 

 vantages of wide planting. These trees were in April, 1912, 

 eleven years of age. Owing to their isolated situation they 

 have had abundant supplies of light and air. The roots of 

 the trees were exceedingly well developed and could be traced 

 to great distances, say over 80 feet. Each tree had a fine 

 spread of foliage. 



Each tree yielded over 100 Ibs. of dry rubber per annum ! 



It can readily be calculated that if one had forty-eight trees 

 to the acre, each yielding 100 Ibs. of dry rubber per annum, 

 the total yield per acre would be 4800 Ibs. As 400 Ibs. per 

 acre is considered a very good yield from closely-planted trees, 

 it will be seen that, if such yields could be obtained from 

 widely-planted trees, i acre of widely-planted trees would be 

 equal to 12 acres of trees closely ; planted. 



Supposing, however, it were to be claimed that the three 

 trees were unusually fine specimens and the yield from them 

 abnormal. Yet it can scarcely be contended that it was due 

 to the trees themselves, and not to the advantages of wide- 

 planting that they enjoyed, that the yields of latex were so 

 enormous. 



It seems reasonable to argue that the ample room which 

 these trees possessed to develop their roots in the soil, and the 

 abundant supplies of light and air which they enjoyed, had 

 a great influence upon the matter. Admitting freely that all 



