Section Pedilonum

Dendrobium section Pedilonum (Blume) Lindl.,
Edwards's Bot. Reg. 30, Misc. 62 (1844) 65.

Rhizomes short to elongated. Pseudobulbs very short to much elongated, wiry to usually distinctly fleshy, with one to many internodes, 1- to many-leaved. Leaves sheathing at the base, except apparently in Dendrobium nothofagicola, rarely papillose (Dendrobium cuthbertsonii), short- to long-lived. Inflorescences lateral or subterminal, mainly from the upper part of the stem, racemose or 1-flowered, usually short and dense. Flowers small to medium-sized, resupinate or not, long-lived (sometimes up to six months), often brightly coloured. Mentum long and usually narrow, often spur-like, parallel with the ovary. Lip not mobile, entire, with a long narrow base; sometimes with a small transverse callus in the basal part, but never with distinct longitudinal keels or lamellae; apex sometimes sharply incurved and hood-like and then often with dentate to fringed margin (mainly in the former section Calyptrochilus). Ovary sometimes sharply winged or conspicuously papillose (in certain members of the former section Oxyglossum).

Burma, Thailand, Indochina, Indonesia, the Philippines, Papua New Guinea, Solomon Islands, Vanuatu, Fiji, Tonga, Samoa. About 150 species; in New Guinea about 120 species (probably less than 100 after revision).

Epiphytes in lowland and montane to subalpine forest. At high altitutes also terrestrial or lithophytic. From sea-level up to about 4000 m altitude.

Section Pedilonum contains some of the most colourful of all flowering plants. Almost any colour of the spectrum can be observed in representatives of this section, including blue, violet, green, and scarlet. While sect. Pedilonum is rather uniform in the shape of the flowers, all having a simple lip with a long narrow base, the vegetative parts vary extensively among the various species, from a tiny mat-forming creeper like Dendrobium parvulum to a robust cane-like plant like Dendrobium smillieae. In New Guinea, it is the second largest section of Dendrobium after sect. Grastidium, but that depends also on the circumscription of the section. Most authors, ourselves included, used to distinguish three or four sections: Pedilonum sensu stricto, Calyptrochilus, Oxyglossum, and Cuthbertsonia. The last two were merged by Reeve & Woods in their masterly revision of sect. Oxyglossum. In the course of preparing this CD-ROM our slumbering doubts about the possibility to distinguish these sections became wide awake when we tried to prepare a key to the sections that really worked. This proved to be an impossible task.

Section Calyptrochilus is supposed to differ from Pedilonum by the hood-like inflexed apex of the lip, which is often pleated and more or less distinctly toothed or fimbriate. There is, however, a complete series of intermediates from species with a flat lip apex to those with upright margins, and finally to those with a really hooded apex. The following picture should prove this point: PEDILON.JPG . Where does Pedilonum end and Calyptrochilus start?

Section Cuthbertsonia is even more weakly defined: the only distinguishing feature being the dwarf habit of the plants in combination with the relatively large flowers produced singly or in pairs. The flowers are not essentially different from such Pedilonum species as Dendrobium pseudoglomeratum and Dendrobium andreemillarae, and an even more dwarf habit is seen in Dendrobium leucocyanum, an undisputed Pedilonum.

Section Oxyglossum, if we exclude sect. Cuthbertsonia, consists of dwarf plants characterised by the very sharply tipped labellum and usually but not always distinctly angular to winged ovary. Again, these character states are in our opinion merely extremes in a continuous series. We can refer to the same picture as above, and rest our case.