133 



wherever you notice a small hole, cut some of the corn and push 

 it in and always pack level. Continue to pack evenly until you 

 have used all your corn then cover the top with one foot of grass 

 spread evenly and pile on all the stones and logs you can get on 

 top to weigh down the stack. 



After you have got on the weights take down the wattle and 

 draw away the side poles and so leave the stack free to settle 

 down. 



The stacking of the corn may take from two to three days and 

 the ensilage will be ready for use in about two months time. 



THE CULTURE OF THE CENTRAL AMERICAN 



RUBBER TREE, X.* 



{Continued from Bulletin for April.) 



By O. F. Cook, Botanist in charge of Investigations in Tropical 



Agriculture, U. S. Department of Agriculture. 



AGE AT WHICH PLANTED TREES MAY BE TAPPED. 



The earliest age at which Castilloa trees may be tapped with 

 safety and advantage has been stated all the way from four to 

 twelve years, while from eight to ten years is the conservative 

 estimate. At the same time it must be admitted that little in the 

 way of positive knowledge exists on this point, and careful expe- 

 riments may be necessary to determine whether, for example, the 

 taking of half a pound of rubber from each treee in the sixth year 

 will retard growth so as to diminish the yield of succeeding years. 

 As the trees approach maturity and have occupied most of the 

 available space, as much may be taken as will not weaken the 

 tree and shorten its life. 



The inferior quality of the rubber obtained from young trees 

 also lessens the inducement for tapping them. It has been known 

 for several years that the rubber and gutta-percha obtained from 

 young plants or from the leaves and twigs of the trees is different 

 from that yielded by a trunk of mature age, in that a smaller or 

 larger percentage of rubber is replaced by non-elastic, brittle, or 

 sticky substances commonly referred to as " resins." Dr. C. O. 

 Weber has recently published the following results of analyses of 

 samples of rubber from trees varying in age from two to eight 

 years : t 



Resins in rubber from trees — Per cent. 



2 years old '... 42. 33 



3 years old ••• 35-02 



4 years old ••• 26.47 



5 years old ... 18.18 



7 years old ... 11-59 



8 years old ... 7-21 



» Extract fnun the U. S. Department of Agriculture, Bull. No. 40. Bureau of 

 Plaat Industry. 



t Tropical Agriculturist, 22 ; 444. January,. 1903. 



