November i, 1906.] 



THE INDIA RUBBER V/ORLD 



43 



THE SOURCES OF THE LATEX OF RUBBER. 



IN a lecture before a number of rublier planters at Ratna- 

 pura, Ceylon, Mr. Herbert Wright, of the government 

 experiment station at IVracieniy discussed at length 

 the construction and formation of the channels from 

 which latex — the rubber liquid — is obtained from the trees. 

 Tlie lecturer exhibited, under the microscope, sections of 

 Hevea seedlings, to illustrate " where the rubber comes 

 from." In these could be .seen the embryonic parts of the 

 giant rubber trees, and the origin of the latex (milk) tubes 

 traced out. There could be seen a mass of minute and more 

 or less regular boxes or cells in the bark, the material from 

 which the future latex tubes arise ; running frequently 

 throughout that beautiful network were long irregular strands 

 of deeply stained tissues connected here and there with cross- 

 bands to form a contorted ladder like structure — that is the 

 laticiferous system — a system only in so far that it is irregu- 

 larly connected at various points, and composed of latex cells 

 brtubes in all their stages. In a well grown tree, by the way, 

 the latex tubes run nmre or less vertically up and down the 

 stem. 



With the growth of the plant, the latex tubes arise and 

 become filled with the globules of the different substances 

 which ultimately give the rubber of commerce. Here and 

 there can be seen the breaking down of cells and the produc- 

 tion of a single tube by the disappearance of partition walls. 

 This decomposition, essential for the production of latex 

 tubes in the Hevea, continues throughout the life of the tree. 

 What seem normal and regular cells in the bark to day may 

 begin to show perforations to-morrow, and within a few 

 Weeks a sy.stem of milk tubes niaj- arise in an area which, had 

 it been tapped too early, would never have yielded a drop of 

 rubber. 



Essential points to be considered are (1) that the latex 

 tubes arise by the perforation and decomposition of ordinary- 

 cells of the bark ; (2) that the processes involved require an 

 interval of time for their completion ; and (3) that in tap- 

 ping operations a series of channels are dealt with which 

 have no very vital association with other parts of the bark. 

 As for the latter point, it is ridiculous to compare the lati- 

 ciferous system of the rubber trees with the circulatory sys- 

 tem of human beings. The lecturer would rather compare 

 the importance of latex to the plant with human hair, which 

 can be regularly removed, and as regularly- reappears. Hence 

 no matter how much latex is removed, the tree continues to 

 flourish, provided the tapping is done with proper care. 



The bark of a growing tree is formed from within out- 

 wards ; new cells are continuallj- being formed which push 

 the older ones outward. All these cells, at some time or 

 other, are liable to undergo decomposition and to assist iu 

 the production of latex tubes. And the material now con- 

 stituting part of the dead dry bark of untapped rubber trees 

 was originally part of the inner bark and probably contained 

 latex. 



It is not in the extraction of latex that harm is done to 

 trees so much as in the removal of the bark containing that 

 suustance. The bark, or cortical tissue, which is removed 

 in tapping does contain organized systems of elements which 

 are of vital importance to the tree. If removed too quickly- 



the life of the tree is endangered. If all the cortical tissue 

 is removed — that is, if the bark from all sides of the tree — is 

 removed oftener than once in three or four years, the result 

 is likely to be fatal. 



During ordinary tapping operations the cortical cells are 

 cut into while in a living condition, and removed at a "time 

 when they contain food intended for the use of the plant. 

 The sooner it is realized that the bark is really the " mother 

 of rubber, " the better it will be for all concerned, since its 

 removal means a reduction in subsecjuent yields. Hence the 

 importance of not tapping too frequently. 



It might be supiJosed that if the latex were not extracted 

 it would become more concentrated, and more rubber would 

 be contained in a given volume of latex. But in the case of 

 some Hevea trees at Heneratgoda tapped for the first time at 

 the age of 30 years, the first tappings, which drew out what 

 might have been considered the concentrated caoutchouc 

 emulsion of many years, gave rubber of inferior quality. 

 The same feature has been observed in rubber from younger 

 trees when tapped for the first time, and whatever the cause, 

 the results do not encourage one to leave mature trees alone 

 for too long an interval, with the idea of getting a higher 

 quality of latex at a subsequent date. Mr. Wright was in- 

 clined to think that if the latex could be extracted by some 

 method that would not destroy the cambium or the bark 

 (cortex), the tree could be drained almost dry of latex with- 

 out being affected injuriously. 



The amount of yield does not always correspond to the 

 number of tappings. The trees in one area tapped daily for 

 a certain period — for 264 times — gave an average of 9 pounds 

 of dry rubber each, while similar trees tapped 131 times, on 

 alternate days, gave an average of 11 pounds. In the first 

 case, all the original bark had been removed, and in the 

 latter only half the original bark. There is ground for be- 

 lieving that, when incision of the latex tubes is made more 

 perfect than at present, the interval between tapping opera- 

 tions may, with advantage, become still longer and yet be 

 accompanied with a further increase in yield and saving of 

 labor. 



The lecturer did not discuss the various methods of tap- 

 ping applied to Hevea in Ceylon, but felt that fuller series of 

 results than are now available would, in view of the present 

 knowledge of the origin and construction of latex tubes, en- 

 able many- important questions to be answered satisfactorily. 

 Summing up, he said : " The latex tubes and their contents 

 require an interval of time to form or accumulate; if they 

 are tapped too frequently they are less turgid and the yield 

 therefrom is reduced ; if the bark is removed too quickly, 

 either by too frequent or too extensive tapping, the material 

 whereby latex tubes might have subsequently developed is 

 completely severed. If you leave the bark on the tree for a 

 certain interval, probably more latex tubes will be formed 

 and the yield per unit of excised bark increased." 



Egypt. — A United States consular report says : "Rubber 

 tires are in constant demand because the blazing Egyptian 

 sun soon wears them out. The importations of automobiles 

 and motorcycles in 1905 were valued at j;i76,ooo. " 



