Dendrobium section Rhizobium Lindl.,
Paxton's Fl. Gard. 1 (1850-51) sub t. 27.
Rhizome elongated, creeping or pendulous. Pseudobulbs distant, consisting of one internode, very short, cylindric, not thicker than the rhizome, 1-leaved. Leaves without sheathing base, glabrous, terete or bilaterally flattened, often pendulous, thick coriaceous. Inflorescences subterminal, racemose, few- to several-flowered. Flowers small to medium-sized, resupinate or not, fleshy, often short-lived. Mentum short, open in front. Lip not mobile.
Lesser Sunda Islands, New Guinea, Australia, Solomon Islands, Vanuatu, New Caledonia, Fiji, Samoa. About 30 species; in New Guinea c. 9 species.
Epiphytes in savannah and in lowland and montane forest.
Section Rhizobium is one of the easiest of all to recognise, even without flowers. Each shoot carries only a single leaf, which in the majority of species is long, pendulous, and terete. Dendrobium rigidum deviates from the others in having a broad, laterally flattened leaf, which is very fleshy and leathery. In recent years this section is often regarded as a separate genus, Dockrillia. We prefer to keep a broader defined genus Dendrobium, rather than to elevate almost each section to generic rank.