Monographs Details:
Authority:
Thomas, William W. 1984. The systematics of Rhynchospora section Dichromena. Mem. New York Bot. Gard. 37: 1-116.
Thomas, William W. 1984. The systematics of Rhynchospora section Dichromena. Mem. New York Bot. Gard. 37: 1-116.
Family:
Cyperaceae
Cyperaceae
Description:
Subspecies Description - Culms erect or occasionally arching, (4-)6-45 cm tall, 0.3-0.9 mm in diameter, green, obtusely triquetrous, glabrous to puberulent; leaves mostly basal or produced within 4 cm of the base; leaf blades (2.5-)4.5-27 cm long, 1-5.5 mm wide, green, flat to occasionally involute, ciliate to very sparsely so on margins, glabrous adaxially, glabrous to puberulent abaxially; leaf sheaths 1-4 cm long, green, nerved, glabrous to puberulent; summit of inner band concave, hyaline, glabrous to ciliate; inflorescence bracts green, 3-5 exceeding inflorescence, ciliate basally along margins (Figs. 3b, 22a); basal bract longest, 2-12 cm long, 1.2-4 mm wide; inflorescence (Figs. 13c, d) a congested head of ca. 4-15 spikelets; spikelets ovoid, 5.5-8 5 mm long, 2-4 mm wide, consisting of ca. 8-16 scales; scales white, often ferrugineously streaked, 3.7-6 mm long, 1.6-3.4 mm wide, ovate, cymbiform, puberulent to glabrous abaxially, carinate distally, often ciliolate along keel; filaments 4 8-5 8 mm long; stigma and style 4-4.4 mm long; stigma branches 1-3.1 mm long; achene (Fig. lid) lenticular, bilaterally symmetrical, stramineous to orange-brown or black, very widely obovate to depressed obovate, 0.9-1.2 (-1.4) mm long, (1.05-)1.15-1.5 mm wide; summit of achene ± irregular, shallowly arched, horizontal or doubly concave (appearing somewhat like an upturned moustache); shoulders of achene at edge of style base usually forming a distinct angle, or at least a discontinuity with the margin of the achene; style base very shallowly triangular (often with rounded or upturned ends) or shaped like an upturned moustache, 0.2-0.4 mm high, 0.9-1.4 mm broad; achene surface strongly transversely rugose; epidermal cells of achene narrowly elliptic to linear, distinct. Flowering and Fruiting: all year. Distinguishing Features: Rhynchospora pubera (including ssp. parvulo) can be distinguished from other species by its cespitose habit, slightly spreading spikelet scales and characteristic, large, strongly rugose achenes. Rhynchospora pubera ssp. pubera can be told from ssp. parvula by its larger achenes, longer spikelets and usually longer culms. These differences are discussed further under ssp. parvula.
Distribution and Ecology - Habitat: invariably on acid, usually sandy soils, in open, usually disturbed areas, and edges of streams. Distribution: (Fig. 20) scattered throughout northern South America, primarily east of Colombia and Peru.
Subspecies Description - Culms erect or occasionally arching, (4-)6-45 cm tall, 0.3-0.9 mm in diameter, green, obtusely triquetrous, glabrous to puberulent; leaves mostly basal or produced within 4 cm of the base; leaf blades (2.5-)4.5-27 cm long, 1-5.5 mm wide, green, flat to occasionally involute, ciliate to very sparsely so on margins, glabrous adaxially, glabrous to puberulent abaxially; leaf sheaths 1-4 cm long, green, nerved, glabrous to puberulent; summit of inner band concave, hyaline, glabrous to ciliate; inflorescence bracts green, 3-5 exceeding inflorescence, ciliate basally along margins (Figs. 3b, 22a); basal bract longest, 2-12 cm long, 1.2-4 mm wide; inflorescence (Figs. 13c, d) a congested head of ca. 4-15 spikelets; spikelets ovoid, 5.5-8 5 mm long, 2-4 mm wide, consisting of ca. 8-16 scales; scales white, often ferrugineously streaked, 3.7-6 mm long, 1.6-3.4 mm wide, ovate, cymbiform, puberulent to glabrous abaxially, carinate distally, often ciliolate along keel; filaments 4 8-5 8 mm long; stigma and style 4-4.4 mm long; stigma branches 1-3.1 mm long; achene (Fig. lid) lenticular, bilaterally symmetrical, stramineous to orange-brown or black, very widely obovate to depressed obovate, 0.9-1.2 (-1.4) mm long, (1.05-)1.15-1.5 mm wide; summit of achene ± irregular, shallowly arched, horizontal or doubly concave (appearing somewhat like an upturned moustache); shoulders of achene at edge of style base usually forming a distinct angle, or at least a discontinuity with the margin of the achene; style base very shallowly triangular (often with rounded or upturned ends) or shaped like an upturned moustache, 0.2-0.4 mm high, 0.9-1.4 mm broad; achene surface strongly transversely rugose; epidermal cells of achene narrowly elliptic to linear, distinct. Flowering and Fruiting: all year. Distinguishing Features: Rhynchospora pubera (including ssp. parvulo) can be distinguished from other species by its cespitose habit, slightly spreading spikelet scales and characteristic, large, strongly rugose achenes. Rhynchospora pubera ssp. pubera can be told from ssp. parvula by its larger achenes, longer spikelets and usually longer culms. These differences are discussed further under ssp. parvula.
Distribution and Ecology - Habitat: invariably on acid, usually sandy soils, in open, usually disturbed areas, and edges of streams. Distribution: (Fig. 20) scattered throughout northern South America, primarily east of Colombia and Peru.
Discussion:
Schoenus pubescens Kunth, in Humboldt, Bonpland & Kunth, Nov. Gen. et Spec. 1: 228. 1815, nom. illeg. Dichromena erostris Nees, Linnaea 9: 291. 1834, nom. nud. Dichromena humboldtiana Nees (excl. var. 7), in Martius, Fl. Bras. 2(1): 111. 1842, nom. illeg. Dichromena unicolor Salzmann ex Steudel, Syn. Pl. Cyperacearum 136. 1855. Type: Brazil, Bahia, Salzmann s.n. (US, lectotype, chosen here; MO, isolectotype). Rhynchospora humboldtiana Grisebach, Fl. Br. West Ind. Isl. 577. 1864, nom. illeg. Rhynchospora pubera var. multispiculosa Kükenthal, Bot. Jahrb. Syst. 75: 308. 1951. Type: Brazil, Pará, 28 Dec 1907, Baker 132 (F, lectotype, chosen here; M, NY, isolectotypes). Pollination: Of the green-bracted taxa I observed, R. pubera ssp. pubera was the most actively and consistently visited by insects (Figs. 13c, d; 14a, b, c). The table below gives the locality, plant voucher collection number, and species of insect visitor. Visitors to Rhynchospora púbera ssp. púbera Surinam: Hanover savanna; Thomas 2398: Trígona (Tetrágono) dorsalis beebei T. (Trígona) fulviventris guianae Lasioglossum (Dialictus) sp. Surinam: Brownsberg Mt.; Thomas 2359: Trígona (Tetrágono) dorsalis beebei T. (Tetrágono) portol T. (Trígona) fulviventris guianae Ceratina sp. Venezuela: T. F. Amazonas: Maroa; no voucher: Trígona (Trígona) hyalinata Pereirapis rhizophila Discussion: Very rarely, specimens of R. pubera with short stolons occur (e.g., Steyermark 57728 from Venezuela). They are similar in habit and habitat to specimens of R. reptans and R. papillosa. They occur near running water and are less pubescent than typical R. pubera. Except for the short, easily overlooked stolons and diminished pubescence, they do not differ from typical R. pubera and therefore do not warrant taxonomic status.
Schoenus pubescens Kunth, in Humboldt, Bonpland & Kunth, Nov. Gen. et Spec. 1: 228. 1815, nom. illeg. Dichromena erostris Nees, Linnaea 9: 291. 1834, nom. nud. Dichromena humboldtiana Nees (excl. var. 7), in Martius, Fl. Bras. 2(1): 111. 1842, nom. illeg. Dichromena unicolor Salzmann ex Steudel, Syn. Pl. Cyperacearum 136. 1855. Type: Brazil, Bahia, Salzmann s.n. (US, lectotype, chosen here; MO, isolectotype). Rhynchospora humboldtiana Grisebach, Fl. Br. West Ind. Isl. 577. 1864, nom. illeg. Rhynchospora pubera var. multispiculosa Kükenthal, Bot. Jahrb. Syst. 75: 308. 1951. Type: Brazil, Pará, 28 Dec 1907, Baker 132 (F, lectotype, chosen here; M, NY, isolectotypes). Pollination: Of the green-bracted taxa I observed, R. pubera ssp. pubera was the most actively and consistently visited by insects (Figs. 13c, d; 14a, b, c). The table below gives the locality, plant voucher collection number, and species of insect visitor. Visitors to Rhynchospora púbera ssp. púbera Surinam: Hanover savanna; Thomas 2398: Trígona (Tetrágono) dorsalis beebei T. (Trígona) fulviventris guianae Lasioglossum (Dialictus) sp. Surinam: Brownsberg Mt.; Thomas 2359: Trígona (Tetrágono) dorsalis beebei T. (Tetrágono) portol T. (Trígona) fulviventris guianae Ceratina sp. Venezuela: T. F. Amazonas: Maroa; no voucher: Trígona (Trígona) hyalinata Pereirapis rhizophila Discussion: Very rarely, specimens of R. pubera with short stolons occur (e.g., Steyermark 57728 from Venezuela). They are similar in habit and habitat to specimens of R. reptans and R. papillosa. They occur near running water and are less pubescent than typical R. pubera. Except for the short, easily overlooked stolons and diminished pubescence, they do not differ from typical R. pubera and therefore do not warrant taxonomic status.