144 HENRY G. SMITH. 
melting point, its indifferent action to ordinary solvents, 
and the fact that its elasticity is not destroyed by heating 
at a high temperature below its melting point. If 
EKucalyptus caoutchouc could be obtained in quantity it 
seems reasonable to suppose that it would have considerable 
commercial value. The small percentage amount, however, 
makes it, at present, of scientific value only, without taking 
into consideration the difficulty of collection, its rapid 
change, and that it only occurs at certain times of the year. 
One cannot, however, refrain from the suggestion that 
from its composition and formation it must be closely 
associated with some of the members of the terpene group 
of essential oils found in the Kucalypts, particularly those 
boiling at a high temperature. If the polymerisation of 
these terpenes into caoutchouc could be accomplished—a 
result perhaps not impossible—then the supply of raw 
material in Australia would be practically unlimited, and 
obtainable from species of Eucalyptus at present unworked 
for their oil constituents. 
Although found in plants belonging to numerous genera, 
this is probably the first time that caoutchouc has been 
shown to occur in any member belonging to the Myrtacee. 
