17 



also be growing ? Careful comparative experiments might be 

 necessary for an answer, and this might differ for different 

 localities. 



EFFECT OF SHADE ON FORM OF TREE 



There are great and persistent differences of shape or " habit" 

 among trees. The Lombardy poplar and the weeping willow are 

 not distant relatives. It is a general fact, however, that forest trees 

 are taller and more slender than those of the same species grown 

 in the open. The low spreading habit, which is desired and 

 encouraged among fruit trees, is not desirable in rubber-producing 

 species, where a large expanse of trunk is needed to supply the 

 milk and to give opportunity for tapping without the necessity of 

 wounding the same place too often. Castilloa trees growing alone 

 in the open often send out permanent branches 8 or 10 feet from 

 the ground, while those in the forest may have from 20 to 40 feet 

 of smooth trunk before the permanent branches are reached. Open- 

 grown trees may have large spreading branches, while in the 

 forest or under close planting the main axis of the tree continues 

 to grow upward and the lateral branches are relatively small. 



The problems of rubber culture may prove in this respect to be 

 directly opposite to those of coffee, where the formation of much 

 wood in proportion to leafage is a sign of unfavourable conditions 

 or of bad plantation management. It does not follow, however, as 

 some have seemed to suppose, that forest shade is necessary to 

 grow long-trunked trees. In coffee culture it is plain that the most 

 wood is formed not by shade culture, but by planting close in the 

 open, and the older-planted trees of Castilloa at La Zacualpa, if 

 not as slender and as smooth-trunked as those of the forest, are 

 certainly tall and slender enough to furnish ample evidence that 

 open culture does not cause a low, spreading growth, if the trees 

 stand close enough together. The Zacualpa experiment is of 

 further significance in this connection, because it shows that a 

 harmful degree of crowding was by no means reached. In 

 numerous instances where from three to five trees grew in a cluster 

 their trunks were each equal in size to those of many of their 

 neighbours which stood alone. '' 



Coffee trees which stand too close together lose the use of their 

 lower branches, which become interlaced and shade one another, 

 and ultimately only the top of each tree continues to grow and 

 produce fruit. The planter must choose a middle course between 

 the injury of his bearing trees by crowding and the waste of 

 capital and labour in keeping clean unused land between trees 

 planted too far apart. With the rubber tree the seed is a con- 

 sideration entirely secondary to the growth of the trunk. In 

 comparison with coffee it may be said that the crowding of rubber 

 trees is desirable, and that it finds its limit, not in the discourage- 



* Planting in clusteis might lie a<lvisal>Ie on sorae accounts, since the trees would 

 better shade their trunks and tlie ground under them, hut the difficulty of properly 

 tapping such trees would seem to exclude this method of culture. 



