The resistance to heat at 80° all well preserved, the 5 year old 
trees rather better than the others. Messrs. Michelin consider that 
there is practically no difference between these, samples. However 
they were not large enough for exhaustive experiments. 
A third suggestion has been that the dfferences in soil and 
climate between South America and Tropical Asia is the cause of the 
difference between the two rubbers. M. Petit (Encyclopedic Roret 
Caoutchouc et Gutta Percha) compares the position of linseed as 
produced in Russia, India and the Argentine, the oil of which has 
different properties and qualities in these different countries, and 
suggests a parallel in rubbers. 
M. Gerber states that the rubbers of different regions of Amazo- 
nas have different values and puts it thus: there are crus de 
caoutchouc comme il y a des crus de vin” (ie— there are vintages of 
rubber as there are vintages of wine). However, he says it is possible 
and probable that these differences are due to various causes, local 
methods of preparation, skill and care on the part of the operator, etc. 
Besides the balls of rubber are marked with the name of the maker 
and those that bear certain marks are the ones most valued and 
sought for. May not, says M. Vernet, each tree produce rubber 
possessing its own individual properties? This occurs in other trees 
and probably also in Tara Rv. u ^r. 
Another suggestion not made by M. Vernet, but which he will 
doubtless refer to in the continuation of the series of articles is that 
the rubber tree that we cultivate in Asia is a different strain or variety 
from that now supplying the bulk of the Amazonas rubber. 
, Practically all the Asiatic trees sprung from one lot of seed 
’collected at Tapajos, but nowadays the bulk of the South American 
rubber comes from a much more remote district and it is certainly 
probable that the tree would vary in different districts and its pro- 
duce would equally vary. Specimens of the plants from the areas at 
present worked have been received at Kew and they appear identical. 
It does not follow, however, from this that the rubber would be 
identical. An expert in rubber from Brazil visiting the Botanic 
Gardens at once identified the tree and rubber as what was formerly 
known as Tapajos, or low river rubber, and stated that it was not 
considered as good as Bolivian. 
With respect to the analysis showing that rubber from young- 
trees is not richer in resins than that from old trees, and to the state- 
ments sometimes made that for commercial purposes young is as 
good as old, if the preparation is equally good, one would receive this 
with caution in view of the great difference in strength and pull of 
the two. Evidently much more chemical research is wanted in the 
matter. — E d. 
