Vol. VIII. Xo. 19-5. 



THE AGEICULTUEAL NEWS. 



327 



THE RESIDUAL RUBBERINTAPPEDTREES. 



The milky juice (latex) which yields the rubber of 

 commLTce is a waste )iroiluct, as far as, the plant which 

 secretes it is concertieil : that is to sa3',*it can no lontjer 

 be converted into products useful in 'nutrition or the 

 provision of enert;y. In any method of tapping, 

 a certain amount of this latex must, remain behind in 

 the tissues of the plant. An explanation of what 

 becomes of this is given in the following abstract, 

 which is taken from the Tropical Agricidtnrist for 

 October 1909:— 



It is generally believed that all the rubber which is 

 formed in the stem of a tree accumulates ioi the latex-bearing 

 tissue until the planter chooses to tap it ; that if he does not 

 tap until the tree is eight years old, he will obtain all the 

 rubber which was in the tree when it was, say, six years 

 old, plus the amount which has formed in Uie additional two 

 years. From a botanical standpoint this is iijiiprobable. After 

 the stem has passed its green stages, it acquires the normal 

 .secondary cortex with a dead corky layer on, the outside; and 

 as it grows older, this corky layer increases in thickness. But 

 the corky layer is formed from the latex-bearing layers. This 

 is readily seen when a tree is pared; the exposed latex-bearing 

 tis.sue is then rajiidly covered by a new corky layer, which is 

 obviously formed from it. Further, if a tree is tapped by the 

 full spiral method, with spirals 1 foot apart,, and the tapping 

 is stopped after a breadth of 6 inches has been cut away 

 along each spiral, the original bark left between the spirals 

 will, in some cases, scale otf in flakes dov.'n to thelevel of the 

 renewed bark. I have taken off scales of brown bark 10 

 inches long, which were formed between two spirals. Now, 

 the brown, corky layers, and the scales just referred to, were 

 originally laticif'erou.s, and the current belief as.sumes that 

 this latex was transferred inwards to the inner bark when the 

 corky layer was formed. But if the brown) scales of corky 

 bark are pounded uj) in a mortar, and then extracted with 

 carbon bisulphide, it is found that they contain an appre- 

 ciable quantity of rubber. .Just as in the case of the leaves, 

 therefore, rubber is discarded with the brown bark, and thus 

 the current belief is shown to be incorrect. When latex- 

 bearing bark is converted into corky bark, the latex which 

 it contains dries up, and the rubber is left in the dead layer. 

 Some of the rubber which was in the tree at the age of si.x 

 is undoubtedly rendered unavailable before the tree is eight 

 years old. The amount might be estimated if the rate of 

 growth of bark were known ; it cannot be a very considerable 

 quantity when the tree is young. ! 



It appears, therefore, that the tree is always discarding 

 rubber as well as manufacturing it, the balance being, of 

 course, in favour of the latter process. This obviously con- 

 tradicts the idea that the rubber from a six-year old tree is 

 itself six years old, or that rubber extracted) from an eight- 

 year old tree is necessarily older than that extracted from 

 a six-year old tree. However, this contradiction is superfluous, 

 for it is evident that in any tree most of the latex is derived 

 from near the cambium in the present systems of tapping, and 

 that that latex in the most recently formed. 



This is not intended to .serve as an argtiment in favour 

 of early tapping. That interpretation of the exi)eriment 

 would involve the confusion of two distinct theories, viz., (1) 

 that all the rubber formed is stored in the laticiferous tissue, 

 and so ' matures ' there, and (2) that the rubber formed at the 

 age of six is as ' strong ' as that formed at the age of 

 eight. The experiment proves that the first of these is, at 

 least in part, incorrect ; it gives no information whatever 

 with regard to the .second. 



HOW EEL WORMS^ ARE SPREAD. 



As eel worms are capable *bf doing much damage to 

 plants and are difficult to eradicate from soil which is infest- 

 ed by them, it is important to know how they may be 

 prevented from spreading to .soil wdiich is comparatively free 

 from them. This ^subject is dealt with in Bulletin Xo. 6 of 

 the Division of Pathology and l^hysiology, Hawaii, from 

 which the following extracts are taken. Other information 

 in connexion with these pests will be found in the Agri- 

 ridtuyal News, Vols. Ill, p. 28-3; VI, p. 123; VIII, pp. 

 138, 280. 



The disease will usually spread from a centre of infec- 

 tion at the rate of a few rods each year. In such cases its 

 progress is through the soil, andi may be marked by its 

 effects on roots. Rut the infection does not always occur in 

 this manner. During a .spell of dry weather, the eggs and 

 dried up larvae exposed on the surface of cultivated ground 

 may be whirled aloft by the wind and scattered for miles 

 over adjacent territory. The disease may thus, unseen, 

 spread by leaps, making itself felt however in the new locali- 

 ties only after some years have elapsed, and when the worms 

 have become abundant by natural increase from the few 

 eggs or larvae deposited by the wind. These facts indicate 

 sufficiently the rate at which root-gall may be spread by the 

 wind. The facts are much the same as for Ti/hnchns 

 devniitaf>'ir, a nematodefortunately so far unknown in Hawaii. 



The different means by which the disease may pass 

 from one piece of land to another deserve careful considera- 

 tion, for upon them may be based a number of useful 

 lirocautions. The migrations due to the worm's own muscu- 

 lar powers are not rapid or great, in fact they are so slight 

 that it may be rjuestionable whether they would account for 

 anything but the very slowest spread of the disease. Even 

 when the worms pass from plant to plant in the same field, 

 it is (piestionable whether the movement is not due to 

 transportation by some of the numerous agencies constantly 

 at work in their neighbourhood. ■ Almost everj'thing that 

 moves either in or upon the soil may transport the minute 

 eggs and larvae of eel worms. Air, water, animals, are all 

 agents in disseminating the disea.se. The general lay of the 

 land determines largely the nature and direction of the 

 watei-currents in the soil. These doubtless have something 

 to do with the spread of the disease. Here very little can 

 be suggested beyond a proper system of drainage. 



(..)ne set of agencies in the spread of root gall, and 

 a most important one, too, has not yet received attention. 

 Insects, earthworms, birds, domestic animals, man him- 

 self, are all factors in the life-history of the eel worm. 

 The insect that burrows in the ground and brings to the 

 surface subterranean material is active in aiding the eel 

 worm in finding new victims. The egg or larva leaves the 

 mandibles of the insect only to be caught up by the wind, or 

 to be pressed with other matter into some crevice in boot or 

 hoof, and thus, it may be, travel miles before being again set 

 down. This is no fancy sketch: every statement rests on the 

 most unimpeachable observation. Even the hands when soiled 

 from field work may carry enough material to start ». thriving 

 colony of eel worms. It only needs to be washed off, and 

 tlirown with the water around the roots of some favourite 

 plant to form a nucleus for a new infected area. But enough 

 has been said to put those interested on their guard. The 

 thorough cleansing of boots and hoofs before passing from 

 infested land to uninfested land is too obvious a precaution to 

 need mentioning. 



