VEGETABLE AND ANIMAL PRODUCTIONS. 349 
and leaves it standing till the next morning. He now pro¬ 
cures a quantity of the stem of the moon-plant ( Calonyc- 
tion speciosum ), pounds it into a mass, and throws it into 
a bucket of water. After this decoction has been strained, 
it is added to the rubber milk in the proportion of one 
pint to a gallon, or until, after brisk stirring, the whole 
of the milk is coagulated. The masses of rubber floating 
on the surface are now strained from the liquid, kneaded 
into cakes, and placed under heavy weights to get rid of 
all watery particles.” It is true that either very heavy 
weights are not handy, or the honest Indian wishes to 
sell water at the price of rubber; for the masses, as I have 
examined them freshly brought in for sale, contain a large 
quantity of water held mechanically in the interstices. 
Alum is sometimes used to coagulate the milk, but is 
thought to render the gum hard and less elastic. A full- 
grown tree should yield about eight gallons of milk when 
first tapped, — which is equivalent to sixteen pounds of 
rubber, worth from ten to twelve dollars. Although the 
law of Guatemala forbids the tapping of young trees, and 
tries to regulate the frequency of the attack, it is ineffect¬ 
ual to prevent the gradual destruction of the wild trees 
through improvident bleeding, and only the establishment 
of private plantations will prevent the final extinction of 
this most valuable source of rubber. The Para rubber 
(.Hevea brasiliensis ) grows only in swamps unfit for culti¬ 
vation ; the true rubber ( Ficus elastica ), so popular a house- 
plant, does not seem to thrive and yield a supply of rubber 
away from its native East Indies; and the Ceara rubber 
of South America ( Manihot Glaziovi) is not of easy culti¬ 
vation, so that the Castilloa certainly promises to be the 
tree, of the many known to produce rubber, most likely 
