phyllaries

Phyllaries are the bracts that form the involucre, the protective envelope around the capitulum (flower head) in most members of the Asteraceae. They are also called involucral bracts. The involucre typically consists of one or more whorls of phyllaries; outer phyllaries are usually larger and more conspicuous, while inner ones encircle the receptacle. Phyllaries vary in shape, texture, and color, and may be green, purple, or brown. They can be free or partly fused and may persist around the fruit or wither away.

Structure and variation: Phyllaries range in form from linear to broad and deltoid, and may be herbaceous, papery, or hardened. The number of whorls and the degree of fusion between phyllaries differ among genera. The margins may be toothed, ciliate, or smooth, and pigmentation can contribute to the overall appearance of the flower head.

Function and development: Phyllaries develop before the florets and protect the developing capitulum from desiccation and predation. After flowering, the involucre may persist around the fruit, contributing to the protective structure around the seed and sometimes influencing dispersal by its physical form.

Taxonomic significance: Because phyllary number, arrangement, shape, and marginal features vary among taxa, they are important in identifying and classifying members of Asteraceae. They help distinguish genera and species in many groups, complementing other vegetative and floral characters.

Etymology and terminology: The term phyllary derives from Greek phyllon (leaf) and the suffix -ary, reflecting their leaf-like bract character. Involution of this structure is central to the concept of the involucre that encloses the flower head.