4 oo SCIENCE PROGRESS 



Dutch in Java considerable cultural attention in the past, and 

 where growing now on any estate the trees are a valuable 

 asset, as the rubber when well prepared commands a price 

 only a little lower than fine Para. It is, however, likely to be 

 replaced gradually by Hevea. Its banyan nature is a drawback 

 to easy tapping, and in other respects it is inferior to Hevea. 



The only other arborescent form of possible value for culti- 

 vation seems to be Funtumia elastica of tropical Africa. Attempts 

 to grow it, however, have not met with much success, and 

 Hevea is being introduced into West Africa in its stead. 



The Landolphias are unlikely to become a cultivated source 

 of india-rubber, as they are climbers (lianes) of slow growth. 



Experience all points to Hevea brasiliensis as the best tree 

 for cultivation. Manihot may take its place in drier tropical 

 regions. Castilloa, Ficus, and possibly Funtumia might be 

 useful as subsidiary sources, and be grown as trees in protective 

 belts on estates. 



General Cultivation 



It is not within the scope of this article, nor is it within the 

 writer's province, to deal in a complete manner with the general 

 cultivation of the Para-rubber tree. However, as this is a crop 

 of a special and novel kind, a few remarks respecting its 

 peculiarities and the problems it offers for solution may not be 

 without interest. 



Close v. Wide Planting— Hevea is a forest tree, and its culti- 

 vation might therefore be deemed a branch of forestry and so 

 conform to the rules of sylviculture ; but timber production is 

 not the aim, hence close planting with the object of producing 

 long straight poles is not necessarily the best means of growing 

 this tree. 



As the latex (rubber milk) is obtained from the bark of the 

 trunk, the main purpose to be striven after is the production of 

 as large an area of bark as possible in a given time. Further, 

 since the greatest yield of latex is from the basal part of the 

 trunk, thus making tapping above six feet, as a rule, inadvisable, 

 it would seem expedient to grow the tree so as to throw the 

 main increase of girth into the basal six to ten feet of bole. In 

 sylviculture the great length of unbranched stem is secured at 

 the expense of its thickness. As soon as the maximum height 

 has been reached, thinning is commenced, in order to give room 



