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The meristematic portion of the periderm, consisting of one layer of cells that initiate formation of the cork and secondary cortex tissue.



(also cork cambium), a secondary formative tissue of plants, consisting of vacuolated thin-walled parenchyma cells. Phellogen cells, divided by septa growing parallel to the surface of the organ, deposit cork cells on the exterior and phelloderm cells in the interior. Phellogen and its derivatives make up the periderm.

In trunks of willow and apple, phellogen is deposited in the epidermis, while in elder and ash it is deposited in the subepidermal layer. It is deposited in the primary cortex in currant and larch and in the central cylinder in grape. In the roots of conifers and dicotyledons it is deposited in cells of the pericycle located around the conducting tissues, which retain their capacity to divide. A heavy deposit of phellogen in the secondary phloem of woody plants and the development of internal periderms cause the formation of crust.

References in periodicals archive ?
The meristematic cells are distributed among undivided cortical cells and do not form a continuous layer (Schoute, 1902) characteristic of a typical phellogen (Junikka, 1994; Waisel, 1995).
phellogen and vascular cambium were completely restored differentiating from areas near the phellogen and vascular cambium of undamaged portion of the bark into the central region of the callus until they became continuous.
However, callus filled partially the gap formed in the root bark in Bauhinia forficata cuttings and in some areas the vascular cambium was restored from the differentiation of the callus cells becoming continuous with the cambium of intact areas while the phellogen differentiated only in the cut edges of the bark bounding the wound tissue.
forficata root bark developed buds from the healing phellogen formed in the callus periphery.
This new meristem, just as in stems, is called phellogen and leads to the production of cork, a dead tissue that protects the inner tissue from desiccation, mechanical injury, insects, and disease.
Bark is not wood but results from the activities of two lateral meristems: the vascular cambium, which produces phloem toward the outside, and the phellogen or cork cambium, which produces the cork and inner parenchymatous layer called phelloderm.