Two New Species of Combretaceae from Puntarenas, Costa Rica

Abstract

Two new species of Combretaceae are described from Costa Rica. Combretum graciliflorum is related to C. cacoucia Exell and is only the second species of section Cacoucia (Aublet) Engler & Diels known in America. Buchenavia costaricensis is the second species of the genus from Central America and is evidently not closely related to the other (B. tetraphylla (Aublet) R. A. Howard). Combretum assimile Eichler is also reported as new to Costa Rica, from the same area as the above two new species (Osa Peninsula, Puntarenas). Among specimens collected in Costa Rica in 19881991 and recently sent to me for naming by the Missouri Botanical Garden are three taxa new to Costa Rica, two of them new to science. The two latter are the first new Central American Combretaceae to be discovered for many years, indicating the need for further detailed studies of the area in question (Osa Peninsula, Puntarenas). Combretum graciliflorum Stace, sp. nov. TYPE: Costa Rica. Puntarenas: Canton de Osa/Buenos Aires, W part of main ridge of Fila Retinto, along and near trail from Palmar Norte to Jalisco, 8?59.5'N, 83?28'W, 780-960 m, 9 Dec. 1988, Grayum & Herrera 9131 (holotype, MO). A speciebus consectionibus floribus extra dense pubescentibus minoribus angustioribusque differt. Pedicelli 37 mm; hypanthium inferius (cum ovario) 3-4 mm; hypanthium superius anguste curvato-infundibuliforme 1017 mm longum (sepalis 2.5-3.5 mm longis inclusis), 3.56 mm latum; petala usque ad 3 mm exserta, ca. 7 x 5 mm, late elliptica. Liana. Minute stalked glands frequent on leaves and inflorescences. Leaves opposite, 3.5-11.5 x 2.5-6 cm, ovate-oblong, abruptly and shortly acuminate at apex, cordate to rounded-cordate at base, with 5-6 pairs of strongly curved lateral veins, densely reddish brown appressed-pubescent on veins, otherwise sparsely pubescent. Petiole 3-6 mm, densely reddish brown appressed-pubescent. Inflorescence a simple, terminal raceme 6-14.5 cm (not fully elongated). Young stems, rachis, bracts, and outside of flowers densely reddish brown appressedpubescent. Lowest bracts ca. 14 x 5 mm, narrowly elliptic, decreasing in size acropetally. Flowers (from base of pedicel to tip of petals, excluding stamens and style) 18-28 mm. Pedicel 3-7 mm. Lower hypanthium (including ovary) 3-4 mm. Upper hypanthium (including sepals) 10-17 mm, narrowly curved-infundibuliform, gradually widening from base, 3.5-6 mm across at base of sepals. Sepals 2.5-3.5 x 2-3 mm, triangular, acute at apex. Petals ca. 7 x 5 mm, broadly elliptic, pubescent, subacute at apex, exceeding sepals by up to 3 mm. Stamens exserted (but broken off). Style exserted at least 10 mm when mature. The label describes the plant as a coarse liana swooping low in forest, with yellowish green petals. However, the petals have dried very dark, and they and the stamens may have been red, as in most members of the same section; the collectors might have been referring to the sepals. I have seen only one sheet of this species, but it is clearly a member of section Cacoucia (Aublet) Engler & Diels (Exell, 1953). This section contains one American species (C. cacoucia Exell) and probably four species in West Africa (Fig. 1). Combretum graciliflorum is readily separable from C. cacoucia because of its much narrower flowers, and comes closer to some of the West African species in flower shape, notably C. mooreanum Exell, C. stenopterum Exell, and some plants of C. bracteatum (M. A. Lawson) Engler & Diels (especially plants formerly segregated as C. gentilii De Wildeman). However, it is distinct from all of these in details of flower structure. The flowers of section Cacoucia are the largest and most highly developed in the genus, with a long curved upper hypanthium, attaining 4.5 cm long in some plants of C. bracteatum (e.g., the type specimen of C. bucciniflorum Exell). They are mostly red or orange in color, have long-exserted stamens and style, and are probably bird-pollinated. The flowers of the new C. graciliflorum are the smallest in the section. The fruits of the West African species of the genus are 5-winged, the wings being wide and thin in C. bracteatum (including C. gentilii and C. bucciniflorum) and C. platypterum (Welwitsch) Hutchinson & Dalziel, and very narrow and corky in C. stenopterum and C. mooreanum. In contrast, the NovoN 5: 106-108. 1995. This content downloaded from 157.55.39.35 on Wed, 31 Aug 2016 04:19:27 UTC All use subject to http://about.jstor.org/terms Volume 5, Number 1 Stace 107 1995 Combretaceae from Costa Rica