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the volume of liquid in the tree, and is in all probability greatly 

 assisted by its greater fluidity, which enables it to flow longer 

 distances to the cuts, the capillary friction being decreased. The 

 greater humidity of the atmosphere would also tend to the con- 

 tinuation of the flow in the rainy season by preventing the drying 

 or the coagulating of the surface of the cuts, though the importance 

 of this factor has not been determined. 



That the increase of the rubber content of the latex serves as a 

 protection against drought is also rendered somewhat more 

 probable by the fact that Castilloa has several characters serving 

 the same purpose. The development of hairs upon the branches, 

 buds, scales, leaves, flowers, and fruits is much greater than is usual 

 among related plants. The self-pruning of the branches and the 

 rapid covering of the scars are also exceptional and of obvious 

 utility in reducing transpiration, and the prompt falling of the 

 leaves in situations where the water supply becomes deficient 

 shows even better the sensitiveness of Castilloa to drought. 



SIGNIFICANCE OF MULTIPLE TAPPING. 



The latex problem acquires new interest from the recent demon- 

 stration that Hevea, at least, continues not only to yield milk by 

 the daily renewal of the wounds, but that the quantity actually in- 

 creases for several days. This might seem to favour the idea that 

 the latex has a nutritive function, the additional quantities being 

 assembled, as it were, to repair the injury. On the other hand, 

 the supposition that the rubber hinders evaporation would also 

 work equally well and affords the additional suggestion that the 

 greater evaporation from the wound may assist in collecting the 

 rubber about it, the yield increasing as the widening of the wound 

 increases the surface of evaporation until the available supply of 

 latex has been depleted. 



CLIMATE AND RUBBER PRODUCTION. 



A CONTINUOUSLY HUMID CLIMATE NOT NECESSARY FOR CASTILLOA. 



The study of Castilloa furnishes evidence that with this tree 

 there is a relation between climate and rubber production, and that 

 this relation is the opposite of that commonly supposed to exist. 



The vast quantity and high quality of Para rubber have natural- 

 ly given Brazil the chief place in the thoughts of those interested 

 in rubber, and it is one of the best established traditions of the 

 subject that the native home of rubber is in the vast, periodically 

 overflowed valleys of the Amazon and its tributaries ; and the 

 common failure to appreciate the diversity of the rubber-producing 

 trees gave this idea very great acceptance. 



Practical experiments in Central America soon showed, however 

 that Castilloa will not thrive in swamps or where the drainage is 

 deficient and this fact is generally noted as a cultural difference 

 between Castilloa and Hevea, though the need of continuous 

 humidity for Castilloa is still insisted upon. The point has even 



