THE CENTRAL AMERICAN RUBBER TREE 219 



open, the requisite amount of shade being obtained by 

 planting the trees sufficiently closely to shelter one 

 another. This method appears to give the most satis- 

 factory results and it is now generally adopted in 

 Mexico. 



The question as to the best distance at which Castilloa 

 trees should be planted has given rise to considerable 

 discussion. It has been fomid that if the trees are planted 

 too closely then* growth is checked and the development 

 of the stems interfered with as soon as the roots of the 

 adjacent trees meet. On the other hand, if the trees are 

 placed so far apart that they do not afford each other 

 shade, their growth is stunted and the sun scorches and 

 dries up the bark. The method of planting the trees 

 closely at first and subsequently thinning-out, as described 

 above, obviates both these drawbacks and at the same 

 time affords an opportunity for a careful selection of the 

 permanent trees. It is claimed that with proper manage- 

 ment the temporary trees will yield sufficient rubber, 

 before the permanent trees are tapped, to make the plan 

 remunerative. 



Tapping of Cultivated Trees. — The method most com- 

 monly adopted on the Mexican plantations for tapping 

 Castilloa trees is a system of large V incisions, which 

 are sometimes connected by a vertical channel. The 

 V incisions are made from 12 to 18 in. apart and usually 

 extend round three-fourths or so of the circumference 

 of the trunk ; in the case of mature trees the tapping is 

 carried to a height of about 30 ft., light ladders or slings 

 being used when making the higher incisions. The latex 

 is collected in cups placed at the base of each V incision, 

 or, if a connecting vertical channel is made, in a single 

 cup at the base of the tree. Sometimes spiral incisions 

 are used instead of V cuts. 



The half- herringbone system has also been tried in 

 Mexico, but has not been generally adopted. One-half of 

 the tree was tapped at a time, the oblique incisions bemg 

 made 18 in. apart and connected by a shallow vertical 

 channel. The second half of the tree was treated in a 

 similar manner when the first incisions had healed. 



In Tobago a system, introduced by Smith, has been 

 adopted in which a large number of small incisions are 

 made in the trunk by means of a chisel with a specially 



