DISEASES AND PESTS 43 



in the Orient has given such excellent results, and is 

 preferred by very many planters to the various patent 

 knives placed in the market of recent years. The first 

 sign of the disease is the appearance of the mycelium 

 in the form of a blue mould on the tapped cortex, 

 where the cambium is protected only by a very thin 

 layer of bark, or is entirely exposed by wounds resulting 

 from bad tapping. This mycelium develops rapidly 

 from dark spots on the bast tissues to a stage when its 

 filaments cover the wounded area, and thence extend 

 horizontally and vertically to the remainder of the 

 tapped surface. When the disease becomes firmly 

 established, an exudation of sticky matter of a resinous 

 character frequently takes place on the rotting cortex. 

 In low-lying localities, where the soil is cold and damp, 

 the trees are affected to a greater extent than on higher 

 lands with better natural drainage, but the latter 

 conditions are no guarantee of immunity from the 

 pest. The effect of this disease is not very serious as 

 regards the mortality of the trees, but it is of the 

 utmost importance in so far that it weakens the 

 quality of the latex to a marked degree. Moreover, 

 the labour conditions in the Amazon Valley are of such 

 a nature that the methodical treatment of any outbreak 

 of disease is never sufficiently thorough to insure satis- 

 factory results. The experiments made in 1913 proved 

 that in the great majority of cases a healthy bark 

 renewal took place under the diseased cortex after the 

 lapse of a few weeks, but that for several months the 

 proper action of the cambium and latex cells was 

 paralyzed to a very great extent by the injuries sus- 

 tained. Cambium rot is quite well known in the 



