epifoliation

Epifoliation is a plant morphological term describing the appearance of leaf-like structures that arise on the surface of another leaf rather than from the stem apex. The name derives from epi- meaning upon and foliation relating to leaves. It is an uncommon and not universally standardized concept; in many floras it is mentioned only in scattered reports and is sometimes treated as a developmental anomaly rather than a distinct growth form.

Description and variation: In reported cases, secondary foliar outgrowths originate from the lamina or leaf margins and may resemble small leaves or leaflets. These structures can be sessile and persist for varying durations or detach with the parent leaf. The developmental origin remains poorly understood, with hypotheses including localized meristematic activity on leaf tissue, hormonal effects, or mechanical factors. Because epifoliation can imitate other forms of leaf variation or post-emergent growth, it may complicate morphological assessments and taxonomic identifications if not clearly distinguished from normal variation, adventitious growth, or epiphytic colonization on leaves.

Ecology and significance: The rarity of reports and the lack of a clear functional interpretation have limited agreement on its ecological meaning. Epifoliation is not regarded as a common adaptive strategy but rather as an unusual or auxiliary aspect of leaf development that may reflect developmental plasticity in some plants.

See also: Phyllotaxis, leaf arrangement, foliation, epicormic growth, epiphyllous growth.