RHIPIDIUM: A fan-shaped flower cluster.
RHIZANTHOUS: Appearing to flower from the root of the plant.
RHIZOCARPOUS: Having the stems and foliage annual but the underground parts perennial, as in Iris and Gladiolus.
RHIZOID: A plant structure that resembles a root in function and overall appearance, but not in its internal structure.
RHIZOME: Rhizomes are thickened, branching, creeping storage stems. They are solid like corms and tubers, but don't have tunics. (See bulbs, corms, and tubers to distinguish.) Although most rhizomes grow laterally just along or slightly below the soil's surface, some grow several inches deep. Roots grow from the underside of the rhizome, and during the growing season new plants sprout from buds along the top. Rhizomes can be increased by cutting the parent into sections, each containing at least one eye. Cannas, calla lilies, corydalises, and lilies-of-the valley are examples of rhizomes. Some varieties of iris grow from rhizomes; others are true bulbs, while others form fibrous roots like most perennials.