or Culmus, among botanists, a straw or haulm; defined by Linnæus to be the proper trunk of the grasses, which elevates the leaves, flower, and fruit.

This sort of trunk is tubular or hollow, and has frequently knots or joints distributed at proper distances through its whole length. The leaves are long, sleek, and placed either near the roots in great numbers, or proceed singly from the different joints of the stalk, which they embrace at the base, like a sheath or glove.

The haulm is commonly garnished with leaves: sometimes, however, it is naked; that is, devoid of leaves, as in a few species of cypres-grass. Most grasses have a round cylindrical stalk; in some species of Schoenus, Scirpus, cypres-grass, and others, it is triangular.

The stalk is sometimes entire, that is, has no branches; sometimes branching, as in Schoenus aculeatus & capensis; and not seldom consists of a number of scales, which lie over each other like tiles.

Lastly, in a few grasses, the stalk is not interrupted with joints, as in the greater part. The space contained betwixt every two knots or joints, is termed by botanists intermedium, and articulus culmi.

This species of trunk often affords certain marks of distinction, in discriminating the species. Thus in the genus eriocaulon, the species are scarce to be distinguished but by the angles of the culmus or stalks. These in some species are in number 5, in others 6, and in others 10.