awn

awn (Arista), in the flowers of Grasses (q.v.), a solitary pointed bristle, growing either from a glume or a palea. The flowers of some grasses are entirely awnless; in many, the glumes alone are awned, or only one of them; in others, the glumes are awnless, and the palea, or one palea, awned. The awn often appears as a terminal prolongation of the midrib of glume or palea; or it may separate below the point, and is then said to be dorsal; or may be jointed at the base, and free from the joint onwards. It may be straight or bent like a knee, or even twisted, and liable to change when moist. Sometimes it is rough, or even serrate, at the edges, as in barley; and sometimes feathery, as in feather-grass (Stipa), where it is also remarkable for its great length. The characters of genera and species are often derived from the awn, but it is not always invariable, even in the same species, and the cultivated varieties of wheat and oats differ much in being more or less bearded. There appears to be a tendency to the diminution or disappearance of the awn through cultivation. See GRASSES.