Rhynchospora colorata (L.) H.Pfeiff.
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Authority
Thomas, William W. 1984. The systematics of Rhynchospora section Dichromena. Mem. New York Bot. Gard. 37: 1-116.
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Family
Cyperaceae
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Scientific Name
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Description
Species Description - Rhizomatous, glabrous perennial with solitary culms; rhizomes (Fig. 37e) elongate to 14 cm or more, (0.6-)0.7-1.7(-2.1) mm in diameter, stramineous; rhizome scales 1.2-1.6 cm long, their bases encircling the rhizome, their tips acute, cymbiform; internodes 0.5-1 cm long; culms erect, terete, becoming obtusely triquetrous distally, green, 12-76 cm long, (0.4-)0.8-1.4 mm in diameter; leaves 3-7 per culm, cauline although sometimes crowded near the base; distal blades (4.4-)8-40 cm long, (0.6-)0.8-3.2 mm wide near base, gradually tapering to a point, flat to incurved, green to yellowish green, smooth, midrib obscure; distal leaf sheath (2.5-)5-7 cm long, green, the summit of inner band concave to truncate or occasionally slightly convex, hyaline; inflorescence bracts (Fig. 37f) green distally, white basally both adaxially and abaxially, 3-7 bracts exceeding inflorescence; basal bract longest, (2.5-)3.5-18 cm long, (1.4-)2-5 mm wide; white portion (2.5-)9-25 mm long; inflorescence congested, forming a hemispherical to globose head of (5-)10-ca. 50 spikelets; spikelets ovoid, (3-)5-8 mm long, 1.5-2.5 mm wide, with 8-18 scales; scales white, lightly streaked with red basally, ovate, cymbiform, carinate distally, (2.5-)3.4-4.1 mm long; filaments 3.2-4.2 mm long; anthers 1.2-1.6 mm long; stigma and style 2.6-2.9 mm long, 0.05 mm wide; stigma branches 1.8-2.1 mm long; achene (Figs. 7a, b) lenticular, usually bilaterally symmetrical, stramineous to dark brown or castaneous, usually as long as wide, 0.9-1.1 (-1.5) mm long, 0.9-1.4 mm wide; shoulders of achene at the edge of the style base forming a distinct angle, not rounded; style base triangular to shallowly triangular, often with an attenuated tip, greyish-brown to brown, 0.350.7 mm long, 0.8-1.2 mm wide; summit of achene horizontal to slightly arched; achene surface transversely rugulose; epidermal cells of achene narrowly elliptical and distinct. Flowering and Fruiting: usually May through August, in the United States. In southern Florida, Mexico, Central America, and the West Indies it may flower all year. Distinguishing Features: Rhynchospora colorata is characterized by having long slender rhizomes, bracts that are white at the base both adaxially and abaxially, a total lack of pubescence and achenes with distinctively angled shoulders. It resembles two other species, R. latifolia and R. floridensis. It differs from the more robust R. latifolia, however, in that it has slender rhizomes not swollen at the nodes, bracts which taper gradually (rather than narrowing abruptly at the point where the bract changes from white to green), basal bracts less than 5 mm wide at the base with its white portion usually making up less than 30% of the total length (Fig. 34), and achene shoulders which are angled and not rounded. Furthermore, R. colorata and R. latifolia have very different habitat requirements. Rhynchospora colorata is found in open disturbed areas having neutral soils, while R. latifolia is usually restricted to savannas having acidic soils. When they are found in close proximity it indicates a change in soil conditions over a short distance: in one such locale, a 10-meter transect from one population to the other showed a change in both the pH and water table levels, demonstrating the basic difference between the habitat and soil demands of the two species. Rhynchospora floridensis can be distinguished from R. colorata because the former is cespitose and spikelet scale keels and margins of the bracts are ciliolate. In addition, the achenes of R. floridensis are smaller, darker and have less angled shoulders.
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Discussion
Schoenus stellatus Lamarck, Encycl. 1: 741. 1784. Type: Horida (P, holotype, not seen). Rhynchospora stellata (Lamarck) Grisebach, Abh. Königl. Ges. Wiss. Gottingen 8: 271. 1857. The specimen photographed in the Lamarck herbarium at P and on microfiche at MICH is indeed R. stellata, however, it was collected in 1789 by Fraser from “Carol, meridionale.” Scirpus cephalotes Walter, Fl. Carol. 71. 1788. Type: (BM, not seen). Dichromena cephalotes (Walter) Britton, Bull. Torrey Bot. Club 15: 100. 1888. Dichromena leucocephala Michaux, Flora Bor.-Amer. 1: 37. 1803. Type: Carolina and Georgia, Bosc s.n. (P, holotype, not seen; MICH, microfiche of holotype). Dichroma leucocephala (Michaux) Persoon, Syn. Pl. 1: 57. 1805. [orthographic variant]. Rhynchospora leucocephala (Michaux) Bõckeler, Viddensk. Meddel. Dansk Naturhist. Foren. Kjøbenhavn ser. 3, 1: 144. 1869. Rhynchospora drummondiana Steudel, Syn. Pl. Cyperacearum 135. 1855. Type: Louisiana, New Orleans, Drummond 394 (BM, holotype). Rhynchospora stellata forma intercedens Klikenthal, Bot. Jahrb. Syst. 75: 300. 1951. Types: Haiti, Port-au-Prince, Mariani, 1 Mar 1926, Ekman NH5657 (B, holotype; GH, US, isotypes). Pollination: Uphof (1932) observed bumblebees visiting the inflorescences of this species. Because of its close similarity to R. latifolia, which is visited by many species of bees, it is very likely that R. colorata is visited by a variety of other bee species as well. Nomenclature: Whether the specific epithet colorata should be used depends on the interpretation of the type of this Linnaean species. Although Sloane’s illustration (pl. 78, fig. 1) in his Voyage to . . . Jamaica (1707) which Linnaeus cites is clearly R. colorata, the specimen in LINN (collected after 1753) is not. The questions are whether Linnaeus described this species from an actual specimen or solely on the basis of Sloane’s careful descriptions and illustrations and what his concept of the species was at the time he described it. Kükenthal (1951), following the lead of Grisebach (1857), rejected colorata as an epithet because, according to him, there are three species under this name in the Linnaean herbarium. This confusion alone seemed to have been sufficient reason for Grisebach and Kükenthal to reject the name R. colorata. It is unlikely that Linnaeus saw a specimen of this species until after 1753 and that he based his description in Species Plantarum just on Sloane’s work. According to C. D. Adams (pers. comm.), there is no specimen of R. colorata in the Hortus Cliffortianus at BM and the specimen in the Sloane herbarium from which the Sloane illustration of R. colorata was drawn is indeed R. colorata. Furthermore, Linnaeus’s original description, and the description of Sloane which he cites, both mention the bicolored nature of the bracts. Even though he may have broadened his concept of the species after 1753, it seems that when the first edition of Species Plantarum was published, Linnaeus considered white bracts an important character. Therefore, I feel that Linnaeus’s Schoenus coloratus is the same species as that depicted in Sloane’s illustration and that Linnaeus based his description only on Sloane’s work. Discussion: Rhynchospora colorata varies greatly in size, ranging from robust plants approaching R. latifolia in size (Fig. 34) (the differences between these two species are discussed under R. latifolia) to delicate plants with almost filiform leaves and bracts. The most extreme of these narrow-leaved plants (e.g., Webster, Samuel & Williams 10322) are quite distinctive; further study might prove these worthy of varietal status. Apart from this, there are no consistently distinct elements that might deserve infraspecific recognition. With one exception, all specimens of R. colorata and R. floridensis examined are distinct. The exception (Florida: Monroe Co.: Big Pine Key, along Key Deer Blvd S of Watson Blvd, Brumbach 9547 (MICH)) has rhizomes like R. colorata, but very slender, and has the ciliolate spikelet scales of R. floridensis. It is probably a hybrid.
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Distribution
Habitat: Rhynchospora colorata is most often found in open, somewhat disturbed sites, on neutral or slightly basic, sandy soil (pH usually 7-8): pastures, roadsides or dune swales. It is also occasionally found on stream banks with Taxodium, in savannas and in pine flatwoods.
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