Palicourea spathacea (Rubiaceae), an Unusual New Species from Costa Rica

Abstract

Palicourea spathacea, a new species from montane Costa Rica, is noteworthy for its spathaceous calyx. This species seems best placed in Palicourea because it is closely related to several species of this genus. Palicourea is a genus of about 200 species of shrubs and small trees that are widely distributed in the moist tropical regions of the New World. Its distinguishing characteristics are persistent stipules that usually have two lobes or awns on each side and are often united intrapetiolarly as well as interpetiolarly; short, subnodal, fleshy sections of the stem that usually shrink with drying to form constrictions; baccate fruits that are bluish or purplish black at maturity; hemispherical seeds that have several longitudinal ridges on the back and a single longitudinal groove or fold on the inner face; and comparatively long (usually about 8 mm long or longer), bright white or colored corollas that are usually swollen asymmetrically at the base and bear a ring of hairs internally below the attachment of the anthers (fig. lc). Palicourea is closely related to the larger, pantropical Psychotria but differs in the features of the corolla described above. Palicourea spathacea possesses all of these characteristics and, in addition, it has an unusual spathaceous calyx. This feature is otherwise unknown in Palicourea, and it might be argued that this species would be better placed in a new genus emphasizing the unusual calyx. To do this would be to indicate that calyx morphology is more important than the other characters that hold Palicourea together. Within Palicourea, P. spathacea is not an isolated species. It is clearly very similar to P. bella (Standley) Dwyer of western Panama, which has an equally long calyx with five imbricate lobes. Several other species from Costa Rica and Panama, including P. macrocalyx Standley and P. lancifera Standley & L. 0. Williams, show successively longer corollas in a series linking P. bella with the more familiar species of Palicourea with minute calyx lobes. To place this new species in a separate genus would be to make an arbitrary break between species that clearly are very closely related to each other and would obscure far more information than it would convey. Palicourea spathacea, sp. nov., fig. 1.-TYPE: Costa Rica, Cartago, along the trail about 6 km beyond the gate to the meteorology station in Alto Patillos, Tapanti Hydroelectric Project, Utley and Utley 4538 (holotype: DUKE; isotypes: CR, F, US). Frutex; folia laminis ellipticis, abrupte acuminatis, 14-28 cm longis, 4.5-13 cm latis, subcoriaceis, glabris vel glabriusculis, nervis lateralibus utroque lat6re 15-25, petiolis 1-2 cm longis, stipulis 5-12 mm longis, lobis rotundis; paniculae glabrae, cernuae, 5-15 cm longae, 1120 cm latae, pedunculis 3.5-8 cm longis, bracteis ellipticis, 9-20 mm longis, foliaceis, purpureis; pedicelli 15-26 mm longi; calyx 9.5-20 mm longus, foliaceus, spathaceus, purpureus; corolla tubulosa, alba, tubo 32-37 mm longo; antherae 4.5-5 mm longae; semina 6-8 mm longa. Erect shrub or small tree 3-6.5 m tall. Stems quadrate and often channelled, glabrous or sparsely puberulent, with a short fleshy section usually present immediately below each node. Leaves with blades elliptic to slightly obovate, abruptly acuminate, with an acumen 1-1.5 cm long, basally cuneate and usually tapering, 1428 cm long, 4.5-13 cm wide, 1.8-2.4 times as long as broad, subcoriaceous, dark green above and glabrous or sometimes hirsutulous along the midrib, below paler with the lamina glabrous or more often puberulent, the costa, lateral veins, and lesser veins sparsely to densely strigillose with hairs 0. 1-0.2 mm long, the costa sometimes hirtellous or tomentulose as well; lateral veins 15-25 on each side of the midrib, obtusely angled to nearly patent, curving broadly to the margins, extending to them and sometimes forming a weak marginal vein; petioles angled, 1-2 cm long, glabrous or sparsely