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.