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Although many points have been advanced for the profitable- 

 ness of this or that rubber plant in preference to others still all 

 inferences so far have been based on limited experience only. 

 What rubber tree is the best to plant in Hawaii can naturally 

 not be decided upon before more evidence has been obtained. We 

 can only draw some general conclusions by comparing the climatic 

 and soil conditions here with those of other countries, where rub- 

 ber cultivation has reached a more advanced stage, as well as 

 with the conditions obtaining in places where the various rubber 

 plants grow wild. The conditions under which a plant develops 

 in its natural surroundings give the observer a number of points, 

 but it is always difficult to recognize correctly all such conditions 

 existing so that others can be compared with them. Any com- 

 parisons of this kind must be confined to districts in which simi- 

 lar soil conditions prevail, if they are to be in any way correct. 



It is in the tropical zone from about 25° North latitude to 25° 

 South where the rubber producing plants grow. Within this belt 

 the general climatic conditions are more or less smiilar, although 

 naturally local variations sometimes are considerable. We can 

 say that in this zone the temperature varies from 75° to 110° 

 Fahrenheit, and that the average rainfall is about 80 inches. If 

 we make a comparison between Hawaii and other rubber pro- 

 ducing countries we find that this Territory is very close to the 

 northern limit of the natural rubber zone. Roughly speaking, 

 these islands are situated between 19° 10' and 22° 25' North 

 latitude. Now Cuba, for instance, is located between 20° and 23° 

 and it is very doubtful whether rubber can be grown profitably in 

 that island. Haiti is situated between 18° and 20° North lati- 

 tude and rubber has not yet been a success. Jamaica and Porto 

 Rico lie between 18^ and 18° 30', and rubber culture there is of 

 no significance, nor has it been very successful where tried. In 

 Mexico the northernmost point where rubber is being grown com- 

 mercially is Tierra Blanca at 18°, but the rubber at that place is 

 not what it ought to be. The Isthmus of Tehuantepec is gener- 

 ally considered as a good rubber producing district and it does 

 not reach further north than 16°. In the State of Chiapas, in 

 Mexico, which lies between 15° and 16° North latitude, is the 

 home of rubber in Mexico. Guatemala goes as far north as 17°, 

 but in the northern districts wild rubber is not common. The 

 countries in the Orient w^here rubber culture has proved a suc- 

 cess are Ceylon, between 6° and 10° North latitude, and the 



