42 PARA RUBBER. 



allow of the cultivation of Para rubber up to an elevation of 2,900 

 feet. Th? illustrations on Plate 12, Series D, show Para rubber at 

 an elevation of 2,600 feet on Passara Group Estate, Passara, where 

 trees varying in age from 7 to 13 years have given 2 lb. of rubber 

 each during 1905. 



" Very few soils have been analysed from the Province of Uva, 

 but from those obtained from Passara the following information 

 has been compiled. Usually from 17 to 30 per cent, passes the 

 90 mesh, 20 to 30 per cent, the 60 mesh, 7 to 8 per cent, the 30 

 mesh, and sand and small stones form from 40 to 43 per cent. The 

 retentive power of moisture is about 2h. The chemical analyses 

 show the presence of from 7 to 11 per cent, of organic matter, 0* 1 

 to 0" 15 per cent, of nitrogen, 0'06 to 0' 1 per cent, of lime, 0*07 to 

 0*13 per cent, of magnesia, 0'05 to 0'08 per cent, of potash, and 

 from 0*03 to 0'04 per cent, of phosphoric acid." 



Manuring for increasing the Yield of Latex. 



If latex is mainly an excretory or useless product it may appear 

 doubtful as to whether manuring will have a beneficial effect on the 

 rubber-producing capacity of the tree. This is an interesting point, 

 and is well worth considering. 



The latex is obtained from cortical tissues. These areas contain, 

 besides the milk tubes, series of cells which store up food, and others 

 which are directly associated with conducting the materials elabo- 

 rated in the leaves from above downwards to various parts of the 

 plant. These tissues are removed in the course of tapping operations , 

 and their renewal entirely depends upon the activity of the cambium. 

 The cambium produces new wood internally and cortical tissues ex- 

 ternally ; generally the cambium produces these two series of tissue 

 in a definite order, and a large production of woody material is 

 accompanied by a proportionate amount of cortical tissues. As the 

 wood is marked off into annual zones it is therefore possible to 

 compare the rate of growth of trees in different countries by examina- 

 tion of transverse sections of the trees, and indirectly to form some 

 idea of the development of the narrow band of cortical tissues in 

 which the milk tubes are contained. 



The latex tubes form part of the cortical tissues, and an increased 

 leaf activity appreciably affects the elements in this region. The 

 more abundant the foliage, the more rapidly will the food material 

 be built up and the more vigorous will the cambium become. From 

 these and other considerations it may be concluded that if manuring 

 is carried out, so that the growth of the leaves and woody material is 

 appreciably increased, the cortical tissue will be proportionately in- 

 creased in quantity, and there will be a larger number of cells avail- 

 able for transformation into laticiferous tubes. Any manure which 

 affects the growth of the leaves or the wood must have a correspond- 

 ing effect on the cortical tissues. The main object in manuring 

 Para rubber should be to increase the number of cortical cells as 

 rapidly as possible ; this increase is dependent upon the activity of 

 the cambium, though the subsequent condition of the newly-formed 



