Seeds may be sown out-doors in a warm border in spring, or in pans, to be placed either in frames or outside. The old plants of perennial sorts may be cut down after flowering, when young growths will proceed from the base, and the whole may be lifted and carefully divided. Cuttings of the young shoots, taken in autumn or spring, will root freely if potted singly and placed in a cold-frame. They will flower the following season at the same time as the divisions. =Dendrobium.= _Orchideæ._ The methods of propagating these plants have already been mentioned. Where a rapid increase of a new or special variety is required, the pseudo-bulbs that are more than one year old should be cut into lengths, and fastened on orchid rafts, with a layer of sphagnum beneath them. Suspend them in a hot, moist house, if possible, over a water-tank. The advantage of this method is that the young plants do not need shifting after they commence rooting on their own account. The section to which _D. aggregatum_, _D. Jenkinsii_, _D. densiflorum_ and _D. thyrsiflorum_ belong, are best propagated by division. (See under Orchids.) =Dentaria= (Toothwort). _Cruciferæ._ Propagated by seeds or divisions. =Deodar.= See Cedrus. =Desfontainea.= _Loganiaceæ._ Cuttings, placed in a sandy loam, in a gentle heat. =Desmodium.= _Leguminosæ._ Increased by seeds, or by cuttings placed under a frame, in heat. =Deutzia.= _Saxifrageæ._ Commercially, the species are mostly propagated by green hardened cuttings in summer, under a frame. Hard-wooded cuttings may be taken in autumn, and be treated in about the same manner as currant cuttings (see page 58). The deutzias are also propagated by divisions and layers. Some of the dwarf sorts are sometimes forced, to make cuttings for winter use. =Dewberry= (_Rubus Canadensis_ and vars., and _Rubus trivialis_.) _Rosaceæ._ Seeds are handled in the same manner as blackberry seeds. Increased by layers and, like the blackberry, by root-cuttings. Layers are made by simply covering the decumbent canes at the joints. This is the usual method of multiplication. The tips, too, root freely, as in the black-cap raspberries. =Dianella.= _Liliaceæ._ Increased by seeds, sown in gentle heat during spring. By divisions. =Dianthera.= See Justicia. =Dianthus.= See Carnation, Pink and Sweet William. =Dicentra=, Capnorchis, Diclytra (Bleeding Heart). _Papaveraceæ._ The crowns may be divided in early spring, or cuttings may be made of the fleshy roots in short lengths, and placed in sand. The roots should be placed in a compost of sandy loam, in well-drained pots, as soon as the foliage dies off, and transferred to a cold-frame. =Dichorisandra.= _Commelinaceæ._ Propagated by seeds, divisions and cuttings. =Dichosma.= See Agathosma.