Ligule
A ligule is a thin outgrowth at the junction of leaf and leafstalk of many grasses 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 to very long 10-20 mm, it can also be smooth on the edge or very ragged. Some grasses do not have a ligule, for example barnyardgrass.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, 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.
In grass-like plants such as sedges and rushes, ligules are usually absent or poorly developed.