Teretisculum Kumar & S.W.Gale, 2018

Kumar, Pankaj, Gale, Stephan W., Phaxaysombath, Thatsaphone & Fischer, Gunter A., 2018, Cleisostoma schoenorchaefolium (Orchidaceae: Vandeae: Aeridinae), a new species from Lao PDR, Phytotaxa 374 (2), pp. 155-161 : 156

Teretisculum Kumar & S.W.Gale , sect. nov.

Type species:— Cleisostoma schoenorchaefolium Kumar & S.W.Gale

Leaves with a single longitudinal groove, semi-terete in cross-section, apex subulate, distinctly constricted a few millimeters before the apex. Column without wings. Spur cavity septate, divided longitudinally into two parallel chambers. Stipe convoluted, broadest at base along the viscidium, abruptly contracted and recurved above, tapering into a pointed hood at apex. Pollinia attached dorsally on either side of the hood at stipe apex, held parallel to the viscidium. Viscidium collar-shaped.

Etymology:— Meaning ‘somewhat terete’ in reference to the morphology of the leaves, which are round but in fact distinctly grooved.

Taxonomic notes:— The new section Teretisculum is currently represented by a single member, C. schoenorchaefolium . The leaves of this sole member are semi-terete and terminate in a subulate apex. This combination of leaf characters has not previously been described in Cleisostoma . Cleisostoma section Subulatum ( Seidenfaden 1975: 23) contains species with subulate leaf tips, but leaves in that section are dorsoventrally compressed, the spur is aseptate and the stipe is simple. A divided, two-chambered spur cavity is known in one other member of the genus, C. elegans Seidenfaden (1975: 46) , which is placed in section Mitriformes Seidenfaden (1975: 45) , but the leaves of that species are terete and its stipe is mitre-shaped. Comprehensive sampling of species representing this and other sections of Cleisostoma is advocated to test the phylogenetic validity of current infrageneric classification.