Latex and its Functions . 
199 
in nutritive functions, either as a conductor or a storer of 
albuminous matter 1 . A thorough study of the proteids of 
latex is much needed. Such interesting work as that of 
Green 2 , done on latices which had been kept for some time, 
has not the same value as examinations of milk freshly 
drawn from the tree, owing to the liability of these complex 
nitrogenous bodies to change. It is a piece of research 
peculiarly fitted for the tropics, where laticiferous trees, 
which freely yield their milk, abound. The few laticiferous 
plants of temperate climes are mostly herbs, consequently 
the collection of their milk for chemical purposes is very 
tedious and unsatisfactory. 
The latex of Hura crepitans , L. (Sandbox tree) is one well 
worth attention. It exudes copiously from a wound in the 
trunk and appears to contain abundant proteid, which seems 
to be largely globulin. 
II. Oxydases in Latex. 
Several latices, which are pure white when they first issue 
from a wound in the plant, rapidly darken on exposure to 
the air. This is due to the presence of an oxidizing ferment 
or oxydase, which, with the aid of the oxygen of the air, 
acts on some constituent of the latex, changing it to a deep 
brown colouring matter. 
The latex of Castilloa is a good example. It rapidly 
darkens on exposure and dries to an almost black rubber. 
By creaming the caoutchouc particles can be separated from 
the dark beer-like liquid and made into a sheet of nearly 
colourless rubber. By quickly heating the collected latex, 
the darkening is arrested, owing to the destruction of the 
enzyme. 
The latex of Hevea collected from the tree-trunk does not 
darken at all on exposure to the air, and provided that 
moulds and putrifactive organisms are kept away, rubber 
1 Sachs, Physiology of Plants, p. 362. Pfeffer, Physiology of Plants, p. 581. 
3 Green, Proc. Roy. Soc., 1886, No. 242. 
