phragma

Phragma is a biological term derived from the Greek word phragmos, meaning barrier or fence. In biology, the word is used descriptively to denote a barrier, partition, or cross-wall within a tissue or cell. The exact meaning of phragma varies by field and historical usage; it appears most often in older or highly specialized texts.

In botany and plant anatomy, phragma has been used to describe partition-like structures that separate compartments within a plant organ or tissue. In historical discussions of cell division and tissue organization, the term has been applied to walls or septa that divide adjacent cells or chambers. In modern plant biology, more specific terminology such as cell plate, septum, or wall is commonly preferred, but phragma may still be encountered in classical literature or in discussions of developmental stages where a barrier-like structure is described.

Beyond plants, the term has occasionally appeared in paleobotany and mycology where authors use phragma to refer to plate- or barrier-like elements within thalli, fruiting bodies, or other tissue architectures. The core idea remains a barrier or partition, with the precise interpretation dependent on the taxon and historical context.

Related concepts include phragmoplast, a dynamic plant cellular apparatus that guides the formation of the new cell wall during cytokinesis; septum, a general term for a partition between compartments; and wall in tissue terminology. Phragma is thus a historical or descriptive term that highlights a barrier-like feature within biological structures, rather than a single, consistently defined structure.