The British Guiana Exhibition. in 
is by no means uncommon, occurs chiefly in sandy soil. 
The gum, unlike that of most other trees, occurs in 
nearly all cases in the soil at the roots, and very rarely, 
and then only in small quantities, on the bark. Two 
explanations of this fact have been given ; one, that the 
gum exudes from the roots of the tree " in a vertical 
direction in columns or pieces upwards of a foot in 
length;" the other, that it arises " from exudations from 
the branches of the tree dropping in the sand below." 
The true explanation appears to be that the gum never 
separates in any large quantity from the woody fibre of 
the tree until the timber is rotten. Most probably, when 
the fibre of the wood decays, the gum is left unaltered. 
This theory is favoured by the fact that the gum oc- 
curs both in considerable quantity in the soil under the 
growing tree, and in much greater quantity wherever 
a locust tree, now fallen and decayed, once stood. 
In the first case the presence of the gum is due to the 
decay of the fallen branches, just as, in the second 
case, it is due to the decay of the whole trunk. Moreover 
in both cases the gum occurs in long pieces, which 
evidently indicate the longitudinal direction of the 
decayed branch or trunk. As to the value of the gum, 
I may state roughly, that even in Georgetown it will fetch 
£30 or £35 per ton ; so that the very little trouble 
requisite for collecting it is certainly well repaid. In 
one case, enough simiri gum to fill eighteen barrels was 
collected from a single spot where a locust tree had 
once stood. 
Another somewhat similar substance, shown at the 
Exhibition in large quantities, was balata, the hardened 
