Nigella.--These hardy annuals, a species of Fennel-flower, are both curious and ornamental. Perhaps the best known among them is N. Hispanica, or Love-in-a-Mist. They only require sowing in the open in spring--but not before the middle of March--to produce flowers in July and August. Height, 9 in. to 2 ft. Night-scented Stocks.--_See_ "Mathiola." Nolana.--Hardy annuals that are suitable for the border, as they are very showy when in flower. The seed should be sown in spring on a gentle hotbed, and the plants transferred to the garden about the middle of May. N. Atriplicifolia may be sown in the open in the autumn. They flower in July and August. Height, 6 in. to 2 ft. North Borders, Plants suitable for.--Hardy Camellias, Chrysanthemums, black and green Tea Plant, Rhododendrons, Ferns, Red Currants, Morello Cherries, and spring and summer cuttings of all sorts. Nuttallia.--This early-flowering shrub is only hardy in the south and south-west of our country. It requires a light, rich soil, and may be increased by division. Racemes of white flowers are produced during February and March. Height, 2 ft. Nycterina.--Exquisite little half-hardy plants, suitable for pots or rock-work. The seed should be sown early in spring on a gentle hotbed, and the young plants transferred to the pots or open ground at the end of May, using a light, rich soil. Height, 3 in. Nymphaea Alba.--A hardy aquatic perennial, frequently found in our ponds. It flowers in June, and may be increased by dividing the roots. Height, 1 ft. O Odontoglossum Grande.--A most beautiful orchid, delighting in a temperature of from 60 to 70 degrees and an abundance of water during summer, but good drainage is essential. The blooms are yellow, spotted and streaked with venetian red, and are often 6 in. across. The pots should be two-thirds filled with crocks, then filled up with fibrous peat and sphagnum moss. During winter only a very little moisture should be given. Oenothera.--The Evening Primroses are most useful and beautiful plants, well suited for ornamenting borders, beds, edgings, or rock-work. All the species are free-flowering, and grow well in any good, rich soil. The annual and biennial kinds are sown in the open in spring. The perennials may be increased by dividing the roots, by cuttings, or by seed, the plants from which will flower the first season if sown early in spring. They bloom in June and July. Height, 6 in. to 4 ft. Olearia.--These evergreen shrubs thrive in peat and loam, and may be increased by division of the roots. O. Haastii has foliage resembling the Box, and a profusion of white, sweet-scented flowers in summer: a chalk soil suits it admirably. Height, 3 ft. to 4 ft. Omphalodes Verna.--A hardy perennial which may be grown under the shade of trees in ordinary soil. It produces its flowers in March, and is increased by dividing the roots in autumn. Height, 6 in.