LIGULE (Lat. ligula, liuqula, diminutive of lingua, °Lat. 11;11g11(1, tangoes ultimately eon fleeted with Eng. tongue). In general, an out growth front the surface of a leaf or leaf-like organ. In practice the name is applied in three groups of plants. the most conspicuous of which is the grass family. The leaves of grasses have t WO distinct regions. the spreading portion (blade) and that which envelops the stein (sheath). At the juncture of blade and sheath the ligule appears as a more or less conspicuous flap-like outgrowth. The two other groups are the little club-mosses (Selaeinellal and the quill worts (lsoetes). both of wide]] belong to one of the great groups (Lyeopodiales. q.v.) of the fern-plants (pteridophytes). in both of these cases there is an outgrowth from the surface of the leaf, which is particularly prominent in the very young stages of the leaf, and may lie re ga•ded as an embryonic structure. In other eases of such outgrowths the term ligulc is not applied. but the structure is essentially the same.
For example. in some flowers of the pink family there is a two-toothed outgrowth from the sur face of each petal, the five outgrowths encircling the throat of the flower and resembling a small ten-toothed crown, called in consequence a corona. A similar corona is conspicuous in the various species of Narcissus, as jonquils, daffo dils, etc., often forming a striking feature of the flowers. The significance of ligular out growths in the plant economy is quite obscure. In the ease of foliage leaves, as grasses, little club-mosses, and quillworts, they Sevin to be structures that are of service only in the em bryonic stages of the leaf, disappearing entirely fir remaining only as rudiments when the blade is mature. In flowers, as in pinks and species of Narcissus, they add to the floral display, and are doubtless of service in connection with insect pollination.