Flag. I. The common name of a large family of the lowest order of plants, known as algae. These algae have all flagging habits, like the common seaweeds, which are usually fixed to rocks by their roots, while their branches are borne up by the tides, falling again and lying in confused masses one upon another at its recess. The propriety of this homely term is better seen in the ulva or laver, of which ulva latissima, very common on the American coast, having a broad, ovate or oblong, undulated, bright green frond, may be seen lying on the soft ooze at low tide, and floating near the bottom at high water. Enteromorpha, with tubular, membranaceous, green, netted fronds, is still more flaccid, and is easily collected from rocks and beaches, when thrown up by the winds. A rich, dark purple kind (porphyra vulgaris, Agardh) may be frequently noticed on the piles and posts of wharves, hanging loosely down, like broad shreds, growing also on rocks between high and low water mark. Even in fresh water, in running streams, the flags are to be met with, such as batracho-spermum moniliforme (Roth.), with very delicate, branching filaments, composed of violet-colored beads, and having a plumy, flagging aspect.
So the conferva, resembling confused and tangled skeins of silk, have the same appearance; and even in the more highly developed bright crimson and red kinds, or in the fuscous and inelegant fuci, and in the larger forms, equalling in size trees and shrubs, the name of flags is not an inapt one.
II. Besides these lower plants, the name of flag is given to the iris family, which bear conspicuous flowers, some of great splendor. (See Iris.) Ill. The sword flags are stiff, erect, very long-leaved plants, with spikes of extremely showy purple, scarlet, rosy, or white blossoms, and with large fiat tubers (cormi), requiring heat, moisture, and sunshine while growing, but entire rest and dryness when dormant. Natives of the Cape of Good Hope, few garden flowers exceed them in gorgeousness or beauty, and few require so little care. The Belgian florists have succeeded in raising many splendid hybrids and varieties, of every hue; and the flower catalogues afford the names of the choicest of these, which command high prices. Gladiolus communis is hardy enough to survive our winters; it is a slender-growing species, with pretty purplish or crimson blossoms, and this and one or two others found in the south of Europe are exceptional; the rest are natives of the hot regions, particularly of the Cape. The ixias are smaller, dwarf irids or flags, with open, showy blossoms upon spikes, and variously colored.
They are finely suited for winter flowering in greenhouses; their bulbs or cormi are planted early in the autumn; the plants, on rising from the soil, are exposed to the air and light, and on approach of frost placed just beneath the sashes of the roof, where they blossom toward spring. These also require extremes of treatment, being kept perfectly dry and warm when in repose.