cell theory
    n 1: (biology) the theory that cells form the fundamental
         structural and functional units of all living organisms;
         proposed in 1838 by Matthias Schleiden and by Theodor
         Schwann [syn: cell theory, cell doctrine]

Cell \Cell\, n. [OF. celle, fr. L. cella; akin to celare to
   hide, and E. hell, helm, conceal. Cf. Hall.]
   1. A very small and close apartment, as in a prison or in a
      monastery or convent; the hut of a hermit.
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            The heroic confessor in his cell.     --Macaulay.
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   2. A small religious house attached to a monastery or
      convent. "Cells or dependent priories." --Milman.
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   3. Any small cavity, or hollow place.
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   4. (Arch.)
      (a) The space between the ribs of a vaulted roof.
      (b) Same as Cella.
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   5. (Elec.) A jar of vessel, or a division of a compound
      vessel, for holding the exciting fluid of a battery.
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   6. (Biol.) One of the minute elementary structures, of which
      the greater part of the various tissues and organs of
      animals and plants are composed.
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   Note: All cells have their origin in the primary cell from
         which the organism was developed. In the lowest animal
         and vegetable forms, one single cell constitutes the
         complete individual, such being called unicelluter
         orgamisms. A typical cell is composed of a semifluid
         mass of protoplasm, more or less granular, generally
         containing in its center a nucleus which in turn
         frequently contains one or more nucleoli, the whole
         being surrounded by a thin membrane, the cell wall. In
         some cells, as in those of blood, in the am[oe]ba, and
         in embryonic cells (both vegetable and animal), there
         is no restricting cell wall, while in some of the
         unicelluliar organisms the nucleus is wholly wanting.
         See Illust. of Bipolar.
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   Air cell. See Air cell.

   Cell development (called also cell genesis, cell
      formation, and cytogenesis), the multiplication, of
      cells by a process of reproduction under the following
      common forms; segmentation or fission, gemmation or
      budding, karyokinesis, and endogenous multiplication. See
      Segmentation, Gemmation, etc.

   Cell theory. (Biol.) See Cellular theory, under
      Cellular.
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Cellular \Cel"lu*lar\ (s[e^]l"[u^]*l[~e]r; 135), a. [L. cellula
   a little cell: cf. F. cellulaire. See Cellule.]
   1. Consisting of, or containing, cells; of or pertaining to a
      cell or cells.
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   2. porous; containing cavities.
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   3. pertaining to or using a system of transmission of
      telephone signals by radio, in which areas are divided
      into geographical parts (cells), each of which is served
      by a transmitter whose range is limited to that region,
      thus permitting a single transmission frequency to be used
      simulataneously in different parts of the same area.
      Cellular telephones are typically small and battery
      powered, allowing a subscriber with such a telephone to
      carry the telephone in a pocket or purse, over the entire
      area served, and to be contacted by a single telephone
      number. The system became widespread and popular in the
      1980's and 1990's; as, cellular telephones sometimes lose
      their link unpredictably.
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   Cellular plants, Cellular cryptogams (Bot.), those
      flowerless plants which have no ducts or fiber in their
      tissue, as mosses, fungi, lichens, and alg[ae].

   Cellular theory, or Cell theory (Biol.), a theory,
      according to which the essential element of every tissue,
      either vegetable or animal, is a cell; the whole series of
      cells having been formed from the development of the germ
      cell and by differentiation converted into tissues and
      organs which, both in plants and animals, are to be
      considered as a mass of minute cells communicating with
      each other.

   Cellular tissue.
      (a) (Anat.) See conjunctive tissue under Conjunctive.
      (b) (Bot.) Tissue composed entirely of parenchyma, and
          having no woody fiber or ducts.
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