Biology. A thin structure forming a dividing wall or partition between parts of a plant.

Botany. A hollow on the interior surface of a plant cell wall, formed by a discontinuity in the secondary cell wall exposing the primary cell…

Botany. A sieve-like plate on the wall of a plant-cell. (Cf. sieve, n. compounds 3.)

Bot. Applied to those cell-walls at a growing-point which have a direction at right angles to the surface: opp. to periclinal, adj. 2. Also as n.…

A periclinal cell wall or division. Now rare.

see sieve-plate, n. 1.

the space within a pit (sense 16), extending from the pit membrane to the pit aperture.

the relatively thin area of primary cell wall and middle lamella at the base of a pit, esp. when this forms the common partition between the…

the central part of the wall between two adjacent plant cells, which is composed chiefly of pectins.

In some conifers and a few flowering plants: the thickened central part of a pit-membrane.

see quots.

a channel in the secondary cell wall leading to the pit chamber of a bordered pit.

the space between the pit membrane and the overarching secondary cell wall of a bordered pit.

an opening on the inner surface of a secondary cell wall, forming the entrance to a pit cavity.

a structure composed of two pits in adjacent cell walls, separated only by the pit membranes and often serving in the exchange of liquids and gases…

= primary pit field n. at primary, adj. n.compounds.

In a gymnosperm: the network of cellulose strands surrounding the torus of a bordered pit membrane.