This section is from the book "A Text Book Of Materia Medica, Being An Account Of The More Important Crude Drugs Of Vegetable And Animal Origin", by Henry G. Greenish. Also available from Amazon: A Text Book of Materia Medica : Being an Account of the More Important Crude Drugs of Vegetable and Animal Origin.
Latex is the name given to the milky liquid contained in laticiferous tissue. This tissue may take the form of elongated, branching cells (Apocynaceoe, Asclepideoe, Urticaceoe, most Euphorbiaceoe) or of superposed cells with intact transverse walls (many Convolvulaceoe) or of superposed cells the transverse walls of which have been perforated, thus forming laticiferous 'vessels' (Papaveraceoe, many Compositae, Campanulaceoe, Sapolaceoe, some Convolvulaceoe and Euphorbiaceoe, &c). In addition to water, salts, proteids, pectin, gum, fat, wax, enzymes, etc, the latex frequently contains substances of medicinal or technical value, as, for instance, alkaloids (Papaver), caoutchouc (Hevea, Ficus, &c), guttapercha (Palaquium, Mimusops), acrid principles (Euphorbia), etc. It is readily exuded by the plant on incision and may thus be collected and dried (opium, lactucarium, euphorbium) or further treated for the isolation of one or more of its constituents (caoutchouc, guttapercha).