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Iberis.—See "Candytuft."

Ice Plants.—See "Mesembryanthemum."

Ilex.—See "Holly."

Impatiens Sultani.—Half-hardy perennials. May be raised from seed sown early in spring on a hotbed, or later on in a shady spot in the open border; greenhouse culture, however, is more suitable. They bloom in August. Height, 1½ ft.

Incarvilleas.—Ornamental hardy herbaceous plants, of easy culture. They are suitable for the border or the rockery, and will grow in any soil if not too dry and exposed. The tuberous roots may be planted at any time in autumn, 4 in. deep. I. Delavayi makes a fine solitary or lawn plant, its leaves being from 1 to 3 ft. long; the soft rose-pink, Mimulus-shaped flowers, which are carried on stout stems well above the foliage, appearing in May. Care should be taken not to disturb it in spring, and it is advisable to cover the roots in winter with a pyramid of ashes, which may be carefully removed at the end of April. Incarvilleas may be propagated by seed sown, as soon as it is ripe, in light, well-drained soil, giving the young plants protection in a frame during the first winter, with enough water merely to keep them moist. Height, 2 ft.

Indian Corn.—See "Zea."

Indian Shot.—See "Canna."

India-rubber Plants.—See "Ficus."

Indigofera.—Beautiful evergreen shrubs. I. Australis has elegant, fern-like foliage and racemes of pink or purple Pea-shaped flowers in April. I. Decora Alba bears its white flowers in July. They require a sandy loam or peat soil, and greenhouse culture. Cuttings of the young wood planted in sand under glass will strike. Height, 2½ ft.

Insects on Plants.—To destroy insects on plants wash the plant with Tobacco-Water (which see). Or put 1 oz. of quassia chips in a muslin bag, pour on some boiling water, and make it up to I gallon; dissolve 1 oz. of soft soap, add it to the chips, and stir well. Use it two or three times during spring and early summer.

Inula Royleana (Fleabane).—A hardy perennial which flowers in November. It will grow in any garden soil, and can be increased by seeds, or by division of the roots. Height, 3 ft.

Ionopsidium.—These hardy annuals grow freely in any rich, damp soil; a shady position is indispensable. Height, 1/8 ft.

Ipomoea.—These beautiful climbing plants are very suitable for covering trellis-work, or for the pillars or rafters of the stove-house. The seed is generally sown in April on a hotbed or under glass, and the young plants set out in the border of the house in May in light, rich soil. Success is mainly secured by allowing plenty of root-room. The perennial kinds are increased from cuttings taken from the small side-shoots placed in sand in a brisk bottom-heat. If grown in the open they often shed their seed, and come up year after year with but little attention. They make a good contrast to Canariensis. The Ipomoea Horsfalliae, with its bright scarlet flowers, has a lovely appearance, but must be treated as a stove evergreen. This is propagated by layers, or by grafting on some strong-growing kind. It thrives in loam and peat mixed with a little dung, and flowers in July or August. Height, 6 ft. to 10 ft.

Ipomopsis.—A very beautiful half-hardy biennial, but difficult to cultivate. Some gardeners steep the seed in hot water before sowing it; but the best way seems to be to sow it in July in 3-in. pots in equal parts of sandy peat and loam, ensuring good drainage, and place it in a cold frame, giving it very little water. When the leaves appear, thin out the plants to three or four in each pot. Replace them in the frame for a week or so, then remove them to a light, airy part of the greenhouse for the winter. During this period be careful not to over-water them. In spring shift them into well-drained 4-1/2-in. pots, using the same kind of soil as before, and taking great care not to injure the roots; still give the least possible amount of water. If plenty of light and air be given, they will flower in July or August. Height, 2 ft.

Iresines.—Take cuttings of these greenhouse plants in autumn; insert them thinly in 48-size pots filled with coarse sand, loam, and leaf-mould, and place in a uniform temperature of 60 or 70 degrees. When they have taken root place them near the glass. Height, 1-1/2 ft.

Iris.—The Iris is the orchid of the flower garden; its blossoms are the most rich and varied in colour of hardy plants. For cutting, for vases, table decoration, etc., it is exceedingly useful, as it is very free-flowering, and lasts a long time in water. It thrives in almost any soil, though a sandy one suits it best, and is strikingly effective when planted in clumps. It soon increases if left undisturbed. The English Iris blooms in June and July, bearing large and magnificent flowers ranging in colour from white to deep purple, some being self-colours, while others are prettily marbled. The German Iris is especially suitable for town gardens. The Spanish Iris blooms a fortnight before the English. Its flowers, however, are smaller, and the combinations of colours very different. The Leopard Iris (Pardanthus Chinensis)is very showy, its orange-yellow flowers, spotted purple-brown, appearing in June and July. They are quite hardy. The best time for planting them is October or November, selecting a sunny position. Height, 1-1/2 ft.

Isopyrums—Hardy herbaceous plants of great beauty, nearly related to the Thalictrums. They will grow in any ordinary soil, but flourish best in vegetable mould, and in a moist, yet open, situation. They are readily raised from seed, or may be propagated by division of the roots in autumn. They flower in July. Height, 1 ft. to 1-1/2 ft.

Ivy (Hedera).—A deep, rich soil suits the common Ivy; the more tender kinds require a lighter mould. To increase them, plant slips in a north border in sandy soil. Keep them moist through the autumn, and plant them out when well rooted. The following are the principal choice sorts:—Aurea Spectabilis, palmate-leaved, blotched with yellow; Cavendishii, a slender-growing variety, leaves margined with white, with a bronzy shade on the edge; Conglomerata, crumpled leaves; Elegantissima, slender-growing, with silvery variegated leaves; Irish Gold-Blotch, large leaves, blotched with yellow; Latifolia Maculata, large white-blotched leaves; Lee's Silver, silver variegated; Maderiensis Variegata, leaves broadly marked with white; Marmorata, small leaves blotched and marbled with white; Pupurea, small leaves of a bright green changing to bronzy-purple; Rhomboides Obovata, deep green foliage; Rhomboides Variegata, greyish-green leaves, edged with white; and Silver Queen, a good hardy variety.

Ixias.—Plant out of doors from September to December, in a sunny, sheltered position, in light, rich, sandy soil. For indoor cultivation, plant four bulbs in a 5-in. pot in a compost of loam, leaf-mould, and silver sand. Plunge the pot in ashes in a frame or cold pit, and withhold water until the plants appear. When making free growth remove them to the conservatory or greenhouse, placing them near the glass, and give careful attention to the watering. Ixias are also known under the name of African Corn Lilies.