A. excelsa (tall). fl. whitish green, disposed similar to the following. l. abruptly pinnate, 3ft. long, with ten to fourteen pairs of leaflets coarsely toothed at the base, without glands. h. 66ft. India, 1800. A stove tree.
A. glandulosa (glandulous).* fl. whitish green, disposed in large branched, terminal, fascicled panicles, exhaling a disagreeable smell. August. l. impari-pinnate; leaflets coarsely toothed at the base with glands. (The leaves on vigorous young trees are sometimes 6ft. in length.) h. 60ft. China, 1751. This tree grows with great rapidity for the first ten or twelve years, in favourable situations, afterwards its growth is much slower. It is quite hardy, and thrives in almost any soil, though one that is light and somewhat humid, and a sheltered situation, suits it best. It is a very desirable tree for plantations, or to stand singly on lawns, and is easily increased by slips of the roots.
AINSLÆA (in honour of Dr. Whitelaw Ainslie, author of a work on Indian drugs). ORD. Compositæ. Herbaceous perennials, of recent introduction. Although, no doubt, both species will prove tolerably hardy, they should have slight protection during winter. They thrive in light rich soil. Propagated by divisions of the root.
A. aptera (wingless). fl.-head purple, disposed in an elongated spike-like panicle. l. deeply cordate, sinuately toothed; petioles wingless, whence the name. Sikkim Himalayas, 1882.
A. Walkeræ (Mrs. Walker's).* fl.-heads slender, distant, shortly stalked, borne in erect or somewhat nodding racemes; the white corolla-lobes and the red purple anthers make a pretty contrast. h. about 1ft. Hong Kong, 1875. A very rare and graceful species.
AIR. Pure atmospheric air is composed of nitrogen, oxygen, and a very small quantity of carbonic acid gas, all of which are essential to the growth of plants. Air-giving is a term used by gardeners to lessen the temperature of a greenhouse, or to equalise it with that outside. See Ventilation.
AIRA (from aira, applied by the Greeks to Lolium temulentum). Hair Grass. ORD. Gramineæ. Chiefly hardy grasses, of agricultural value. Panicle loose; spikelet compressed, with two perfect flowers, and sometimes a neuter. Of easy culture, in ordinary garden soil. Sow seeds in spring.
A. flexuosa (waved).* The Waved Hair Grass. fl. shining brown; panicle erect, spreading, with waved angular branches and flower-stalks. l. short. Stem upwards of 1ft. high, erect, smooth. England. A very pretty and graceful perennial.
FIG. 54. AIRA PULCHELLA.
A. pulchella (pretty).* fl. panicles loose, very delicate and graceful. l. very short. h. 6in. to 8in. South Europe. An elegant plant, with tufted filiform stems. One of the best of dwarf-growing ornamental grasses. See Fig. 54.
AIR-PLANT. See [Aerides,] also Epiphytes.