Readily increased by seeds, which start better if soaked for a few hours in hot water. Also by root-cuttings. =Gymnogramme.= See Ferns. =Gymnyostachys.= _Aroideæ._ Propagation is effected by suckers and divisions. =Gynerium= (Pampas Grass). _Gramineæ._ Seeds, under glass in the north. Also increased by dividing the tufts. =Gynura.= _Compositæ._ Increased by cuttings and seeds. =Gypsophila.= _Caryophylleæ._ Propagated by seeds, division or cuttings. =Habranthus.= See Zephyranthes. =Habrothamnus.= See Cestrum. =Hackberry.= See Celtis. =Hæmanthus= (Blood Flower). _Amaryllideæ._ Bulbels, which should be removed and potted when the plants are commencing new growth, and be kept in a close pit or house till established. Seeds are rarely used. =Hæmodorum= (Australian Blood-root). _Hæmodoraceæ._ Increased by dividing the roots in spring. =Hakea=, Conchium. _Proteaceæ._ Well-ripened cuttings, placed in sandy peat under glass, in a cool house. Seeds, when obtainable, can be used. =Halesia=, Pterostyrax (Silver-bell or Snowdrop Tree). _Styracaceæ._ Seeds, which rarely germinate till the second year. They should be kept constantly moist. Propagation is also effected by layers, or by cuttings of the roots in spring and autumn. Layers are commonly employed in this country. =Halimodendron= (Salt-tree). _Leguminosæ._ Freely increased by seeds, layers or cuttings. May also be grafted on common laburnum. =Hamamelis= (Witch-hazel). _Hamamelideæ._ All grow from seeds or layers, and the Japan species succeed if grafted on American species in the greenhouse. _H. Virginica_ may be readily propagated by layers. =Hamelia.= _Rubiaceæ._ Seeds. Cuttings which are nearly ripe will root during the early part of summer under glass, with heat. =Hamiltonia=, Spermadictyon. _Rubiaceæ._ Seeds. Half-ripened cuttings, placed in sand under glass. =Hardenbergia.= _Leguminosæ._ Seeds may be used; also increased by divisions. Cuttings, made of the firm young side shoots in spring, will grow if inserted under a bell-glass, and placed in a warm frame or pit, without bottom heat. =Hardwickia.= _Leguminosæ._ Propagated by ripened cuttings in sand, in a strong heat. =Harebell.= See Campanula. =Hatchet Cactus.= See Pelecyphora. =Haw=, Hawthorn. See Cratægus. =Hazel.= See Corylus. =Heartsease.= See Viola. =Heath.= See Erica. =Heather.= See Calluna. =Hedera= (Ivy). _Araliaceæ._