YUCCA, ADAM'S NEEDLE, in botany; a genus of plants of the class hexandria and order monocotyledona. The corolla is campanulate and patent, there is no style, the capsule is triangular. There are four species, none of which are natives of Britain. All of them are exceedingly curious in their growth, and are therefore much cultivated in gardens. The Indians make a kind of bread from the roots of this plant.