Datura.—­Ornamental half-hardy annuals.  The seeds of all the species must be sown on a hotbed early in spring.  When the plants are strong enough transplant them in the border, where they will bloom more freely than in pots.  The seeds of D. Ceratocaula will sometimes remain several years in the ground before they germinate.  They flower in July.  Height, 2 ft. to 3 ft.

Day Flower.—­See “Commelina.”

Day Lily.—­See “Hemerocallis.”

Delphinium (Larkspur).—­The gorgeous spikes of flowers produced by these plants render them invaluable for the border.  They like a deep soil, highly enriched.  The perennials may be divided at the root in autumn, care being taken not to injure the young fleshy sprouts.  The annuals are readily raised from seed.  The quickest way to grow the perennial varieties from seed is to sow in a frame with a slight bottom-heat, at any time from March to August; but sowings made in the open from April to June will succeed.  Keep the ground moist, and shade from the sun till the plants are up, then transplant to nursery beds for the summer, afterwards transferring them to their final quarters.  Flower in June and July.  Height, 1-1/2 ft. to 6 ft.

Dentaria Digitata (Toothwort).—­This tuberous hardy perennial grows well in old leaf-mould, and is very suitable for the base portion of rock-work, where it can obtain both shade from the midday sun and moisture.  It is readily increased by cutting the roots into pieces about 1-1/2 in. long, and replanting them where they are intended to bloom, putting 1 in. or so of sand round them.  They flower in May.  Height, 1-1/2 ft.

Desfontania Spinosa.—­A fine, evergreen wall shrub with holly-like leaves, and long, pendulous scarlet and orange flowers in June.  It grows best in a compost of loam, peat, and sand, with a south or west aspect.  It is propagated by cuttings under glass.  Height, 10 ft.

Desmodium Canadense.—­This is a fine border hardy perennial, producing long racemes of rosy-purple flowers in June or July.  It prefers a soil of sandy loam and peat, and may be increased by seed or by cuttings planted in sand and subjected to heat.  Height, 4 ft.

Desmodium Pendulaeflorum.—­A hardy evergreen shrub, flowering in July.  It thrives in sandy loam and peat.  Cuttings planted in sand with a little bottom-heat and under glass will strike.  Height, 6 ft.

Deutzia.—­A beautiful conservatory shrub, bearing in spring a large quantity of flowers resembling the snowdrop.  A peaty soil suits it.  It is pretty hardy.  Height, 3 ft.

Devil-in-a-Bush.—­See “Nigella.”

Dianthus.—­Very beautiful and fragrant flowers.  The genus embraces Carnations, Pinks, Picotees, and Sweet Williams.  The soil most suitable for them is a light, loamy one, mixed with a little rotten dung and sand.  It is well to confine the rarer kind to pots, so as the better to protect them in winter.  They are propagated by layers, cuttings, or division of roots.  If the cuttings are taken about the middle of June, and placed under glass on a gentle hotbed, they will be ready in about three weeks to plant out in the open.  The annuals and biennials merely require sowing where they are intended to bloom.  Flower in July.  Height, 1-1/2 ft. to 2 ft.