Best grown from seeds. Also increased by layering; or it can be grafted. The European species is often grafted upon the hornbeam (carpinus). =Othonna=, Aristotela, including Doria (Ragwort). _Compositæ._ Very easily propagated by seeds and cuttings. The leaves also take root. =Ouvirandra= (Lattice-leaf). _Naiadaceæ._ The plants are divided, or seeds are used when they can be obtained. =Oxalis.= _Geraniaceæ._ Seeds, divisions and cuttings. The tuberiferous species are increased by the small tubers which form upon the roots. =Oxycoccus.= See Cranberry. =Oxydendron= (Sorrel-tree). _Ericaceæ._ Increased by seeds, which must be handled carefully in light soil. Also by layers, which, however, often root with difficulty. =Oxylobium=, including Callistachys, Podolobium. _Leguminosæ._ Increased by seeds and layers. Cuttings of rather firm side young shoots, made during spring. =Oyster Plant.= See Salsify. =Oxytropis.= _Leguminosæ._ Seeds should be sown where the plants are to stand; also by dividing the plant in spring. =Pachira=, Carolinea. _Malvaceæ._ Seeds. Large cuttings cut at a joint, with the leaves on, in heat. =Pæony= (Peony, Piney). _Ranunculaceæ._ Seeds, giving new varieties, are sown as soon as ripe. The seedlings seldom rise above the surface the first year, all their energies being spent in the formation of roots. The common herbaceous varieties are oftenest propagated by division of the clumps. Each portion should possess at least one bud upon the crown. All woody species may be increased by layers and cuttings. Cuttings are taken late in summer, cut to a heel, and are handled in a frame or cool greenhouse. During winter they should be kept from freezing. The shrubby species and _P. Moutan_ are often grafted, and all species can be handled in this way. The operation is performed in late summer or early autumn, and the grafts are stored in sand or moss where they will not freeze. The next spring they are planted out. The cion is made from a strong short shoot, destitute of flower-buds, and is set upon a piece of root, as described and figured on a previous page (p. 88, Fig. 85). Some prefer to cut a wedge-shaped portion from the side of the stock, in which to set the cion, rather than to split the stock; but either practice is good. Strong roots of various varieties or species may be used. The Chinese pæony (_P. Moutan_), _P. officinalis_ and _P. albiflora_ are probably oftenest used. =Painted-cup.= See Castilleja. =Palafoxia.= _Compositæ._ Seeds, commonly sown under glass, or in mild climates sown in the open. =Palicourea.= _Rubiaceæ._ Cuttings, made in spring under glass. =Paliurus=, Aubletia (Christ's Thorn). _Rhamneæ._ May be increased by seeds, by layers or by cuttings of the roots.