Ligule

A ligule (from Latin: ligula "strap", variant of lingula, from lingua "tongue") — is a thin outgrowth at the junction of leaf and leafstalk of many grasses (Poaceae) and sedges. A ligule is also a strap-shaped extension of the corolla, such as that of a ray floret in plants in the daisy family Asteraceae.

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) to very long 10–20 mm (Johnson grass, 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).

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.

Asteraceae

Asteraceae or Compositae (commonly referred to as the aster, daisy, composite, or sunflower family) is an exceedingly large and widespread family of flowering plants (Angiospermae).

The family has more than 23,600 currently accepted species, spread across 1,620 genera (list) and 13 subfamilies. In terms of numbers of species, the Asteraceae are rivaled only by the Orchidaceae. (Which of the two families is actually larger is unclear, owing to uncertainty about exactly how many species exist in each family.) Many members have composite flowers in the form of flower heads (capitula or pseudanthia) surrounded by involucral bracts. When viewed from a distance, each capitulum may have the appearance of being a single flower. The name "Asteraceae" comes from the type genus Aster, from the Greek ἀστήρ, meaning star, and refers to the star-like form of the inflorescence. "Compositae" is an older but still valid name which refers to the fact that the family is one of the few angiosperm ones to have composite flowers.