14 



tations of Castilloa require the shade of larger trees or may be 

 exposed to full sunlight. The argument that Castilloa always 

 grows in shady locations in nature is by no means conclusive, 

 since it is well known that many forest trees thrive better when 

 they have the opportunity of standing alone and are free from the 

 close competition for food and sunlight implied by forest condi- 

 tions. It is also certain that Castilloa is not only able to obtain 

 an existence in the open, but that it makes much more rapid growth 

 quite without shade than it does in the forest. If the problem 

 were merely to secure the quick growth of Castilloa there would 

 be no hesitation between these two methods of planting ; but there 

 are many stages between dense forest and clean culture, and the 

 question may well be raised whether the conditions most favourable 

 for rubber production are not to be found in some of these. Ad- 

 vocates of both extremes and all intermediate conditions are not 

 lacking, so that the question of shade with Castilloa bids fair to 

 become as complicated and as extensively debated as with coffee 

 and cacao. Moreover, as with those crops, it may be found to 

 have no general solution, but to depend upon local conditions of 

 soil and climate. 



That rubber can be grown under forest conditions there can be 

 no doubt, since all the natural supplies are to be credited to this 

 method of production, but the desirability of forest planting does 

 not necessarily follow, since it is equally certain that under 

 the deep shade the trees grow with an extreme slowness, 

 which would exhaust the patience of any investor. Moreover, as 

 previously shown, it may well be doubted whether a plantation of 

 Castilloa would ever grow to normal maturity in the undisturbed 

 forest ; the indications are that only those trees survive which are 

 able to profit by accidents to their larger neighbours and thus 

 receive more sunlight than usually reaches the undergrowth of a 

 dense tropical forest. In other words, regular forest planting does 

 not mean the placing of Castilloa under conditions most favorable 

 to its growth in nature ; these are more nearly attained when the 

 forest is thinned out or partly cut away. 



Koschny, who distinguishes four kinds of Castilloa in Costa 

 Rica, says that the " hule bianco," or white Castilloa, is the only 

 one adapted for cultivation, and that this is never found in the deep 

 forest, but in more open places, where the foliage has access to 

 the sunlight. 



Experiments with forest planting were studied in eastern Guate- 

 mala and in Southern Mexico, and in both instances the young 

 trees were at an obvious disadvantage in comparison with others 

 planted at the same time in more open situations. Many indi- 

 viduals had hardly grown at all in six months and many had died. 

 On the other hand, it should be explained that the trees, while they 

 had no shade overhead were not exposed to the extent which 

 might be implied by the term "open culture," since they stood in 

 a clearing only a few acres in extent. The neighbouring forest 



