The diseases and pests of the rubber tree . de is tappedout completely, the other is not likely to be attacked byBrown Bast in the meantime. But if the first side is leftwhen, say, six inches have been tapped, the remaining barkmay be found to be attacked by Brown Bast, when it isdesired to return to It. Nodules The development of burrs on the stem of Hevea was firstnoted in the East in 1904, and it is now of common occurrencein aU rubber-growing countries. The affected stems maybear a single, large, more or less uniform swelling on one sideof the tree, extending from the base to a height of t
The diseases and pests of the rubber tree . de is tappedout completely, the other is not likely to be attacked byBrown Bast in the meantime. But if the first side is leftwhen, say, six inches have been tapped, the remaining barkmay be found to be attacked by Brown Bast, when it isdesired to return to It. Nodules The development of burrs on the stem of Hevea was firstnoted in the East in 1904, and it is now of common occurrencein aU rubber-growing countries. The affected stems maybear a single, large, more or less uniform swelling on one sideof the tree, extending from the base to a height of two orthree feet, or a number of smaller, sub-hemispherical pro-tuberances clustered together in an irregular mass. Fre-quently elevated ridges extend from the edge of the largerswellings over the surroimding area of the stem. In the daysof pricker tapping the clustered burrs were the more frequent, NON-PARASITIC DISEASES 181 but at the present time the type generally met with is thesingle large swelling. Where burrs of several years growth. Fig. 22.—Burrs on a Hevea stem. are present, the whole of the lower part of the stem becomesgnarled and knotted, and tapping is impossible. 182 THE RUBBER TREE chap. These swellings are the result of the formation, in thecortex, of a mass of wood, which is generally known as anodule. At first this woody mass is small, and its presenceis only indicated by a slight elevation of the bark; in thisstage the nodule is embedded in the cortex, not united to thewood of the stem, and can be shelled out quite easily witha penknife. Each nodule possesses a cambiimi of its own,distinct from the main cambium of the stem. Consequently,it increases in size by the addition of layers of wood aU roundit; and as it grows larger it causes the characteristic its older stage, or sometimes when the nodule is quitesmall, it develops points on the inner surface which unitewith the main wood of the stem, so that ultimately the woodof the stem and the no
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