MODE OF OCCURRENCE OF CAOUTCHOUC IN THE GUAYULE, PARTHENIUM ARGENTATUM GRAY, AND ITS FUNCTION

In the guayule, as in some other rubber-bearing plants, the rubber occurs in the parenchyma cells and is thus segregated. In contrast with this condition is that in the so-called latex-bearing rubber plants, such as Hevea, Manihot, Ficus, Euphorbia, Scorzonera, ChondriUa, etc., in which the rubber is a constituent, more or less prominent according to the species, of a white or colored milky fluid, which is stored in tubes from which, when opened, the fluid flows more or less freely. The fluid in question is always a complex emulsion of rubber1 and other substances (resins, fats) as the internal phase, with water containing proteins, salts, sugars, etc., in solution as the external phase. The size of the suspensoids differs greatly, and is from 2 microns and less in Hevea and Kickxia to 60 microns or more in