_D. grandiflora_ and others of similar habit are propagated by offsets. These are best taken off about December, and treated like the old plants. (See under Orchids.) =Disocactus.= See Phyllocactus. =Disporum=, including Prosartes. _Liliaceæ._ Seeds may be used; or the plant may be divided in spring before active growth commences. =Dodecatheon=, Meadia (American Cowslip). _Primulaceæ._ Seeds. The crowns may be divided either in spring or autumn. Cuttings of the whole root can be effectively used, the root being torn off the crown, planted upright, and of course covered with the sandy soil commonly used in this form of propagation. =Dog's Bane.= See Apocynum =Dog's-tooth Violet.= See Erythronium. =Dogwood.= See Cornus. =Dolichos.= _Leguminosæ._ By seeds. Sometimes cuttage or layerage is resorted to. =Dorcoceras.= See Bæa. =Doronicum=, including Aronicum (Leopard's Bane). _Compositæ._ Propagated by seeds and divisions. =Dorstenia.= _Urticaceæ._ Seeds may be sown in a hot-bed in early spring. Before active growth commences the plants may be divided. =Doryanthes.= _Amaryllideæ._ Propagated by suckers placed in small pots. =Dorycnium=, including Boujeania. _Leguminosæ._ Increased by seeds. =Downingia=, Clintonia. _Campanulaceæ._ Seeds should be sown in mild heat in spring. =Draba=, including Petrocallis (Whitlow Grass). _Cruciferæ._ The annuals or biennials propagated by seeds sown in spring in the open border. The perennials may be propagated by dividing the crowns. =Dracæna= (Dragon-tree). _Liliaceæ._ Rarely grown from seed. Layers do not succeed very well. The stems of old plants may be cut up in pieces one or two inches long, and placed at any season in cocoanut fiber or light soil, in the bottom heat of a propagating house. The tops of the plants will also strike as cuttings, and the fleshy base of the stem is sometimes removed and used for propagation. Root-cuttings do well in a moderate heat. (See Fig. 47.) =Dracocephalum= (Dragon's Head). _Labiatæ._ The annuals are grown from seeds, sown in the open in spring. Perennials are increased by dividing the roots, or by cuttings of the young shoots in spring. =Dracontium.= See Amorphophallus. =Dragon's Head.= See Dracocephalum. =Dragon-tree.= See Dracæna. =Drimys=, Wintera. _Magnoliaceæ._ Cuttings made of half-ripened shoots should be inserted in a frame. =Drosera= (Sundew). _Droseraceæ._