Definition of ligules:
(n) :
(botany) A portion of a leaf found at the base of the petiole, when present.
(n) :
(botany) In many grasses (Poaceae) and some sedges (Cyperaceae), the membranous appendage or ring of hairs projecting from the inner side of a leaf at the junction between the blade and the sheath.
(n) :
A strap-shaped structure.