A ligule (from "strap", variant of ''lingula'', from ''lingua'' "tongue") is a thin outgrowth at the junction of

leaf A leaf ( : leaves) is any of the principal appendages of a vascular plant stem, usually borne laterally aboveground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", while the leaves, ste ...

and leafstalk of many grasses (Poaceae) and

sedges The Cyperaceae are a family of graminoid (grass-like), monocotyledonous flowering plants known as sedges. The family is large, with some 5,500 known species described in about 90 genera, the largest being the "true sedges" genus ''Carex'' wit ...

. A ligule is also a strap-shaped extension of the corolla, such as that of a

ray floret The family Asteraceae, alternatively Compositae, consists of over 32,000 known species of flowering plants in over 1,900 genera within the order Asterales. Commonly referred to as the aster, daisy, composite, or sunflower family, Compositae we ...

in plants in the daisy family

Asteraceae The family Asteraceae, alternatively Compositae, consists of over 32,000 known species of flowering plants in over 1,900 genera within the order Asterales. Commonly referred to as the aster, daisy, composite, or sunflower family, Compositae w ...

Poaceae and Cyperaceae

The ligule is part of the leaf that is found at the junction of the blade and sheath of the leaf. It may take several forms, but it is commonly some form of translucent membrane or a fringe of hairs. The membranous ligule can be very short 1–2 mm (

Kentucky bluegrass ''Poa pratensis'', commonly known as Kentucky bluegrass (or blue grass), smooth meadow-grass, or common meadow-grass, is a perennial species of grass native to practically all of Europe, North Asia and the mountains of Algeria and Morocco. Altho ...

, ''Poa pratensis'') to very long 10–20 mm (

Johnson grass Johnson grass or Johnsongrass, ''Sorghum halepense'', is a plant in the grass family, Poaceae, native to Asia and northern Africa. The plant has been introduced to all continents except Antarctica, and most larger islands and archipelagos. It re ...

, ''Sorghum halepense''), it can also be smooth on the edge or very ragged. Some grasses do not have a ligule, for example barnyardgrass (''

Echinochloa crus-galli ''Echinochloa crus-galli'' is a type of wild grass originating from tropical Asia that was formerly classified as a type of panicum grass. It is commonly known as cockspur (or cockspur grass), barnyard millet, Japanese millet, water grass, common ...

''). A ligule can also be defined as a membrane-like tissue or row of delicate hairs typically found in grasses at the junction of the leaf sheath and blade. The ligule appears to be a continuation of the leaf sheath and encircles or clasps the stem as does the leaf sheath. The three basic types of ligules are: membranous, a fringe of hairs (ciliate), and absent or lacking. Most grasses have ligules, and the shape, length, and appearance of the ligule margin provide consistent characters for separating genera and some species of grasses. Ray-floret

In grass-like plants such as sedges (

Cyperaceae The Cyperaceae are a family of graminoid (grass-like), monocotyledonous flowering plants known as sedges. The family is large, with some 5,500 known species described in about 90 genera, the largest being the "true sedges" genus ''Carex'' w ...

) and rushes (

Juncaceae Juncaceae is a family of flowering plants, commonly known as the rush family. It consists of 8 genera and about 464 known species of slow-growing, rhizomatous, herbaceous monocotyledonous plants that may superficially resemble grasses and s ...

), ligules are usually absent or poorly developed.

Asteraceae

In members of

, a ligule is the elongated tongue of the corolla of a

ray flower The family Asteraceae, alternatively Compositae, consists of over 32,000 known species of flowering plants in over 1,900 genera within the order Asterales. Commonly referred to as the aster, daisy, composite, or sunflower family, Compositae we ...

ligulate flower The family Asteraceae, alternatively Compositae, consists of over 32,000 known species of flowering plants in over 1,900 genera within the order Asterales. Commonly referred to as the aster, daisy, composite, or sunflower family, Compositae we ...

.Sia Morhardt, Emil Morhardt, California Desert Flowers, University of California Press, pp. 30-32

Clubmosses

The microphylls of

Lycopodiophyta The lycophytes, when broadly circumscribed, are a vascular plant (tracheophyte) subgroup of the kingdom Plantae. They are sometimes placed in a division Lycopodiophyta or Lycophyta or in a subdivision Lycopodiophytina. They are one of the oldes ...

of the families

Selaginellaceae ''Selaginella'' is the sole genus of vascular plants in the family Selaginellaceae, the spikemosses or lesser clubmosses. This family is distinguished from Lycopodiaceae The Lycopodiaceae (class Lycopodiopsida, order Lycopodiales) are an o ...

(spikemosses or lesser clubmosses) and

Isoetaceae Isoetaceae is a family including living quillworts (''Isoetes'') and comparable extinct herbaceous lycopsids (''Tomiostrobus ''Tomiostrobus'' is an extinct quillwort genus from the Early Triassic of Australia, China and Russia, which was espe ...

(quillworts) have minute, scale-like flaps of tissue called ligules at the base of the upper surface of each leaf blade. This feature distinguishes them from clubmosses of the family

Lycopodiaceae The Lycopodiaceae (class Lycopodiopsida, order Lycopodiales) are an old family of vascular plants, including all of the core clubmosses and firmosses, comprising 16 accepted genera and about 400 known species. This family originated about 380 mil ...

References

{{reflist Plant morphology