98 



[August, 1912. 



country we studied plants that grew in a medium we could plough and till and we 

 equipped our laboratory and wrote our text books on the experience gained therein. 

 In a tropical country with a good rainfall like Ceylon, nature works in a laboratory 

 of her own, exceeding in dimensions everything with which we have had any 

 previous experience. We must enter her laboratory as students, remembering that 

 she yields up her secrets grudgingly. Some years ago I sent home a sample of soil 

 to Dr. Voelker, consulting chemist to the Royal Agricultural Society of England. 

 He reported that the soil was completely impoverished, deficient in all the in- 

 gredients of plant food, and it was a wonder anything grew upon it. I replied that 

 the soil supported a rich clove plantation, and added that it seemed to me that in 

 the tropics soil was of less importance than a proper balance of sun and rain; and 

 he answered that, when in India the same thought had occurred to him. We 

 have brought in for exhibition some rubber, the product of one month's tapping of 



A HEVBA TREE AT HENARATGODA, 



It weighs 18 lb. This tree goes on yielding in that proportion six months or more 

 in the year. In 3$. years it yielded 275 lb. of rubber. What is the cause of this? I 

 have heard it described as a freak, but I do not accept that solution. If we had 

 been planting rubber for a hundred years, or if this tree stood in a plantation of 

 100,000 others of like age and size, we might be justified in regarding it as a freak ; 

 but there are only a few trees on the island that can rank as its peers, and these are 

 grouped round it. It is one of the original consignment imported from Brazil, 

 lhis tree has never been manured : therefore manure has had nothing to do with 

 its remarkable yield. It grows on rather poor soil : therefore its abundant flow of 

 latex is not due to exceptional richness of soil. We can thus eliminate three 

 influences : individual peculiarity, manure, soil, and say that none of these has had 

 anything to do with the rich return of this Hevea tree. What remains ? To what 

 other conditions is vigorous tree growth due ? 



LIGHT, AIR AND ROOM 



are three, and this tree, standing on the outside of the plantation, enjoys a liberal 

 supply of all of these. Leaves cannot perform their functions without light, and 

 other things being equal we may take it that the more light they receive during the 

 hours of daylight, the more work they will do and the more vigorous will the 

 circulation of the tree become. The same may be said of air , while it will be 

 obvious that the less the soil preserves of a tree are encroached upon by neighbours, 

 the greater will be the stores of plant food at its disposal to draw upon. But the 

 most important factor of tree vitality yet remains to be indicated, namely, moisture. 

 In the tropics fertility follows in the track of the rain ; and one of the functions of 

 rain is to keep the water table at its normal level. It is not unlikely that this large 

 and vigorous Hevea may have succeeded in tapping subterranean reservoirs as yet 

 out of reach of its companions. Now if this is so and had this tree been subjected to 

 systematic manuring, root development might have been encouraged towards the 

 surface instead of towards the deeper layers of the soil, and it. that case the water 

 table might never have been reached. We have here then a hypothetical case, and 

 it seems to me not at all an unreasonable one, in which 



MANURING MIGHT ACTUALLY HAVE DONE HARM, 



instead of good. You cannot, of course, argue from one tree, especially a tree that 

 is a generation older than most rubber trees on the island ; I have only taken it to 

 illustrate the point I wish particularly to make, which is, that in the presence of 

 natural forces working so very much more vigorously than we have been accus- 

 tomed to intemperate climates, where the science of agriculture has been built up, 

 it is possible we may be devoting too much attention to what I will term the arti- 

 ficial side of rubber cultivation— manuring and methods of tapping, and that we 

 might achieve better results at first by devoting our energies more to removing 



