stoma

1. Stoma
   (Anat) One of the minute apertures between the cells in many serous membranes.
2. Stoma
   (Bot) The line of dehiscence of the sporangium of a fern. It is usually marked by two transversely elongated cells. See Illust. of Sporangium.
3. Stoma
   (Bot) The minute breathing pores of leaves or other organs opening into the intercellular spaces, and usually bordered by two contractile cells.

1. (n) stoma
   In zoology, a mouth or ingestive opening; an oral orifice; an ostium or ostiole: chiefly used of small or simple apertures, as a cytostome; hence, also, a small opening of any kind through which something may pass in or out; a pore. Specifically— An opening of a lymphatic vessel; a lymphatic pore or orifice, as an interstice between the cells of a serous membrane.
2. (n) stoma
   In botany, a minute orifice or slit in the epidermis of leaves, etc., which opens directly into air-cavities or intercellular spaces that pervade the interior, and through which free ingress and egress of air take place; a breathing-pore. The apparatus of the stoma consists usually of a pair of cells (there are several in the Equisetaceæ, Hepaticeæ, etc.), called guard-cells or guardian-cells, between the opposed concave sides of which lies the slit or opening, which extends through the whole height of the epidermis and permits free communication between the intercellular spaces and the external air. According to Van Tieghem, the stomata are always open in sunlight and closed in darkness. These cells are strongly thickened on the upper and under walls of their opposed faces, while elsewhere their walls are relatively thin. The opening and closing of a stoma depend upon the difference in thickness of the parts of the walls. When the turgescence of the guard-cells increases, they curve more strongly, and consequently the cleft widens; but with decreased turgescence the cleft becomes narrower. See also cut under Iris.
3. (n) stoma
   In Sweden borg's philosophy, a cubical figure with hollowed surfaces, being the figure of the interstices of spheres arranged in what Swedenborg calls the fixed quadrilateral pyramidal position, supposed to be that natural to the spherical particles of water.

1. (n) Stoma
   stō′ma (bot.) one of the minute openings in the epidermis of leaves and tender green stems of plants, subserving the purpose of respiration:
2. (n) Stoma
   stō′ma (zool.) one of the breathing-holes in the bodies of certain of the articulata

stomate pore