X 
INTRODUCTION. 
vessels termed Cmenchyma or laticiferous vessels* and are found 
in the greatest abundance in the 
Mesophlceum or middle layer of 
the hark (Eig, 1). This milk is 
only yielded in quantity suffieaitet 
for commercial purposes by cer- 
tain plants within the isotherms of 
70° Fahrenheit, and with a mean 
annual temperature not lower than 
61° and averaging about 76°, and 
with an annual rainfall not lower 
than about 90 inches. I have ap- 
pended to this Report two maps, 
in order to give some idea of .the 
geographical distribution. The first shows the general distribution 
over the globe (Map I.), and the second that in Assam (Map II.). 
The former must, however, be taken as an approximation to 
the truth, as it is the first attempt to thus illustrate the subject. 
These shrubs or trees are restricted to three natural orders, 
viz. ; BitpJiorbiacece , Artoearpacece , and Apocynacece , and in this 
Report these various plants are treated in this order. 
The following fist gives the geographic and botanic sources of the 
different varieties of Caoutchouc : — 
I. American Varieties : — 
Fig. 1 . — Laticiferous Tissue. 
Brazil : — 
Para. 
Maranham. 
Pernambuco. 
Ceara. 
French Guiana. 
British Guiana. 
Venezuela. 
New Grenada or 
“ Carthagena,” 
Ecuador or “ Guayaquil.’ 
Peru, 
Hevea Braziliensis Mull, arg., &c. 
Hev e<e sps. 
Hancornia speciosaMix\l t arg,, &c. 
Herein sps. 
Hevea Giiyanensis Aubl. 
AT. paucifolia Mull, arg, 
H. Brasiliensis Mull. arg. 
? Castilloa elastica Cerv. 
Castilloa elastica Cerv. 
Castilloa elastica Cerv. 
? Hevea peruviana? 
