1. An outgrowth from the top of the leaf sheath in grasses. It may be a scalelike flap of tissue or a ring of hairs and is often of great diagnostic value. Compare auricle
2. The strap-shaped elongation of the corolla tube in certain florets of the Compositae. The five teeth of the ligule represent the tips of the five fused petals. Genera of the tribe Lactuceae, e.g. Taraxacum, Hieracium, have capitula consisting solely of ligulate florets.
3. An outgrowth from the upper side of the microphyll in species of Selaginella. The sporophylls in the strobili also possess ligules.