74 THE RUBBER INDUSTRY 



backward condition, and after twenty years' growth are 

 frequently under 30 inches in girth at 3 feet from the 

 ground. Although slow development is due in part to 

 neglect to keep them clean from the scrub and weeds 

 choking all progress, it does not account for the marked 

 disparity between the rate of growth in Brazil and the 

 Orient, after making ample allowances for lack of 

 cultivation in the former country. 



The bark renewal after tapping is exceptionally good 

 in all districts of the Amazon Valley. Even when trees 

 are hacked about unmercifully with the machadinho, the 

 cortex makes the most vigorous effort to repair the 

 damages inflicted by the many careless collectors. On 

 trees of all ages tapped with the gouge in 1913, and 

 subsequently attacked on the tapped surface by a most 

 virulent form of cambium rot, the renewal of bark was 

 extraordinary; moreover, it w r as equally strong in the 

 case of forest trees shut out from the free access of air 

 and light, and on those growing close to the river-banks 

 and receiving a full allowance of sunshine. In the 

 Orient, experience shows that deep shade is a deterrent 

 to bark renewal, whereas in the Amazon Valley the 

 evidence available proves that it produces no such 

 effect ; in fact, the idea is deep-rooted in most districts 

 that exposure to the direct rays of the sun causes the 

 latex cells to become barren, and arrests the growth of 

 new bark. It is extremely difficult to reconcile these 

 absolutely reverse conditions of the same tree under 

 atmospheric influences containing practically no differ- 

 ence in the characteristic features of moisture, soil, and 

 temperature, or to attribute them solely to variations 

 resulting from the effects of regular cultivation. 



