Latex and its Functions. 
203 
IV. Difference in properties between the Latex 
of young and old organs of the same Plant. 
While investigating the latex from young stems and leaves 
of certain indiarubber trees, with the object of testing the 
feasibility of extracting commercial rubber from them, it was 
found that in several instances the * rubber ’ obtained was quite 
different from that got from the trunk and main branches. 
This is an important point relative to the production of 
caoutchouc from young organs. 
In the case of Hevea , the rubber collected from the young 
stems and leaves, as well as from the unripe capsules, is 
somewhat adhesive, and has less elasticity and strength than 
that from the trunk. 
In the Castilloa introduced into Ceylon, the latex from the 
stems bearing leaves, as well as from the leaves themselves, 
moulds between the finger and thumb into a very sticky 
substance, wholly unlike the caoutchouc-containing latex of 
the trunk. It dries to a brittle material, which becomes 
viscous when warmed. The quality of the rubber from stems 
of this Castilloa , 12*5 to 25 c.m. in circumference, was likewise 
tested ; it seemed to have properties intermediate between 
that of the shoots and the trunk, being slightly sticky and 
somewhat deficient in elasticity. From all that I have heard, 
the true Castilloa elastica does not exhibit this distinction 
between the shoot and trunk. 
The climbing rubber-plants Landolphia Kirkii and Urceola 
escidenta show a similar difference between the latex from 
the shoot and that from thick stems. 
Ficus elastica also exhibits this peculiarity 1 . Attention 
was called to this in Ficus as far back as 1839 by Weinlung. 
He called the substance ‘viscin/ and considered it inter¬ 
mediate between resin and caoutchouc. 
Perhaps in the foregoing plants the laticiferous tubes 
1 See Weiss, Trans. Linn. Soc. iii, 1892, p. 243 ; also Seeligman, Le Caou¬ 
tchouc et la Gutta-percha, 1896, p. 91. 
