Secretory sacs occur abundantly in the leaflamina, where they appear as short lines between the veins; they are abundant also in the cortex and pith of the shoot, in the fleshy integument of the ovule, and elsewhere.
When taken internally it is both a secretory and an excretory cholagogue, but so irritant and powerful that its use in cases of jaundice is generally undesirable.
The formation of the conducting tubes or secretory sacs which occur in all parts of the higher plants is due either to the elongation of single cells or to the fusion of cells together in rows by the absorption of the cell-walls separating them.
A slender ciliated gullet (e) leads into a large stomach (st) whose wall consists of large richly ciliated cells with usually a pair of simple secretory sacs opening into it: it may open through an intestine or rectum into the cloaca.
Perhaps its most remarkable action is that upon the terminals of nearly all the secretory nerves in the body.