Species Of Xyris Research Articles

New Species of Xyris (Xyridaceae) from Tanzania

Four new species of Xyris, X. ornithoptera, X. mallocephala, X. mentiens and X. porphyrea are described from Tanzania. Xyris ornithoptera is close to X. ednae Lock, X. mallocephala is Xyris sp. C sensu lock (1999), and X.mentiens and X. porphyrea resemble X. schliebenii Poelln. These new taxa confirm the general species-richness of south-western Tanzania and northern Zamhia.

Submicroscopical Features of Leaves of Xyris Species

The leaf ultrastructure of five Xyris species were examined using scanning electron microscope (SEM), transmission electron microscope (TEM) and histochemical methods. All studied leaves show some features in epidermis and mesophyll, which were of considerable adaptative significance to drought stress. Such features included the occurrence of a pectic layer on the stomatal guard cells and the presence of a network of pectic compounds in the cuticle. Pectic compunds were also in abundance in lamellated walls of the mesophyll cells and on the inner surface of the sclerified cell walls of the vascular bundle sheaths. There were also specialized chlorenchymatous "peg cells" in the mesophyll and drops of phenolic compounds inside the epidermal cells.

Systematic vegetative anatomy and ensiform leaf development in Xyris (Xyridaceae)

Ensiform leaf development in monocotyledons follows a broadly similar sequence in a wide range of relatively unrelated taxa, indicating a plastic developmental pattern, possibly associated with stressed environmental conditions, since Xyris species tend to grow in relatively damp but nutrient-poor environments. The bifacial leaf sheath surrounds the apex and the subadjacent primordium. A conical unifacial leaf tip ‘Vorläuferspitze’ is established at an early stage, followed by extension growth in the region behind it, generating a unifacial ensiform blade. Root and rhizome structure are also described in a systematic context, particularly in comparison with related taxa in Xyridaceae and other commelinoid monocotyledons, although information on these structures is relatively sparse.

A New Nematopoid Species of Xyris (Xyridaceae) from Guyana

A new species of Xyris has been found in the wet savanna lands of the Rupununi District, Guyana. Xyris dilatatiscapa is described, illustrat- ed, and discussed as to its relationships with other Xyris.

Notes on the Genus Xyris (Xyridaceae) in East Africa

Two new species of Xyris are described from East Africa. They are Xyris ednae from Uganda and Xyris erosa from Tanzania. Xyris humpatensis var. rhodolepis is raised to specific rank as X. rhodolepis. The typification and status of X. anceps is discussed and two varieties distinguished. The typification and identification of X. welwitschii Rendle is examined. This name has been widely misinterpreted. It is here lectotypified, and a third new species, X. subtilis, described to accommodate Ugandan and Tanzanian material to which the name has been applied.

Intercellular pectic protuberances in leaves of some Xyris species (Xyridaceae)

Mature leaves of eight species of Xyris were prepared by standard methods for electron transmission microscopy. Wartlike intercellular pectic protuberances were observed on the surface of inner periclinal walls of epidermal cells in Xyris obcordata, Xyris hymenachne, and Xyris pterygoblephara. In the latter, the protuberances also occur on the surface of parenchymatic mesophyll cells; they frequently project into intercellular spaces and may connect opposing cells. For the genus Xyris, the intercellular pectic protuberances may be considered taxonomically significant at the species level. Keywords: Xyris, Xyridaceae, pectin, cell wall.

New species of Xyris from Cuba

New species of Xyris from Cuba

Xyris L. section Xyris (Xyridaceae) in Australia

A systematic study of the Australian species of Xyris section Xyris is presented. Seven species are recognised, of which Xyris cheumatophila A.N. Doust & B.J. Conn is described for the first time. All recognised taxa are provided with descriptions (including illustrations), distribution information (including maps), habitat descriptions, nomenclatural and other relevant notes. Lectotypes are here designated for all previously described Australian species of section Xyris which are accepted by us. An iconotype of the name of X. indica (the type of the genus) is here chosen.

A New Species of Nematopoid Xyris (Xyridaceae) from the Araracuara Area of Colombia

A new species of Xyris (sect. Nematopus) has been discovered in the Caqueta basin east of Araracuara, Dept. Caqueta in the Colombian Amazon area. Xyris trachysperma is described, illustrated, and discussed as to its relationships with other taxa of the section. The affinities of X. trachysperma appear to be more with species of planaltan Brazil than with those of the Guayana Highlands. During integrated surveys by personnel of the Tropenbos Program of the forest and soils of the Caqueta basin east of Araracuara, Dept. Caqueta, in the Colombian Amazon area, J. Duivenvoorden and associates visited and collected plants in the savanna complexes of a sandstone meseta (350 m a.s.l.) near Araracuara in 1988 and 1990. This region of Colombia has long been known to be rich in Xyridaceae: its lowland and upland savannas produce a wealth of species shared with the Orinoco and Rio Negro systems of Colombia and contiguous Venezuela and also some unshared endemics. The Araracuara area has had a fairly long history of plant exploration, most of it originating with R. E. Schultes, H. Garcia-Barriga, and associates in the 1950s, and subsequently by B. Maguire and associates in the 1950s and 1960s, resulting in the discovery of several novelties, three from Rio Caqueta savannas. Yet these systems are so large and so complex that the potential for further discoveries continues. Therefore, when a large set of collections from this place was sent from Tropenbos to VDB for definitive study, one Xyris attracted particular attention. A full description of it is provided to emphasize that its affinities are, surprisingly, more with species of planaltan Brazil rather than with its Colombian or Venezuelan cohabitants. Xyris trachysperma Kral & Duivenvoorden, sp. nov. TYPE: Colombia. Dept. Caqueta: Araracuara (0?37'S, 72?24'W), sobre la mesa de areniscas de la base militar, 18 Oct. 1990, Joost Duivenvoorden & A. Cleef 306 (holotype, Herbario Amaz6nico; isotype, VDB). Figure a-n. Xyris trachysperma, species nova: a X. bialata Malme foliis et scapis ciliatis, bracteis fertilibus minute rufociliatis, a X. melanovaginata Kral caulibus brevioribus, scapis bialatis, areis dorsalibus distinctibus, et ab ambobus seminibus paucis (2-4), cupiformis, 1.3-1.4 mm longis, grosse papillatis bitruncatis, bi-umbilicatis, apicibus anguste apiculatis, placentatio basalis differt. Sturdy caespitose perennial to 75 cm high, roots fibrous, somewhat coarse. Stems short, to 4 cm. Leaves flabellately spreading, the principal ones 4060 cm long, longer than the scape sheaths; sheaths entire, ecarinate at base, carinate above it, lustrous brown or dark red-brown, the keel a deep shining red-brown, often rusty-ciliolate, the sides abruptly, then gradually narrowing to a short-ligulate apex; blades elliptic-linear, 3-4 times longer than the sheaths, 5-10.1 mm wide, flat, olivaceous, with several broad, low nerves, the surfaces finely papillose; tips abruptly incurved-acute, densely redciliate; margins with a narrow, deep, red-brown, incrassate, lustrous, entire to intermittently rustyciliolate border. Scapes gradually widening from base upward, broadly bi-alate, distally to 6 mm wide, green, slightly thickened and rusty-ciliolate at margin, the sheaths angulate, short-bladed. Spikes narrowly ellipsoid or cylindric, 1.5-2.5 cm long, obtuse, many-flowered; sterile bracts 2 pairs, decussate, the lower pair triangular, strongly carinate, 3-5 mm long, the carinas ciliolate, the inner pair obovate, ca. 3-3.5 mm long; fertile bracts broadly ovate to broadly elliptic, 6-7 mm long, convex, ecarinate, at anthesis with a light brown matrix, reddish brown, with margin rusty fimbriolate and with the dorsal areas ovate or broadly elliptic, green, with costa indistinctly antrorsely arcuately branched. Flowers with lateral sepals free, curved, inequilateral, ca. 6 mm long, acute to acuminate; keel broad, rustyNOVON 3: 55-57. 1993. This content downloaded from 207.46.13.172 on Sat, 15 Oct 2016 04:43:07 UTC All use subject to http://about.jstor.org/terms

Studies in Xyridaceae II. Two New Species of Xyris from Brazil

Two new species of Xyridaceae, Xyris jolyi and X. coutensis, from Minas Gerais, Grazil, are distinguished from close relatives on the basis of morphological features including bracts, sepals, and leaves.

Xyris Nigrescens Kral, A New Species of Xyris (Sect, Nematopus) from Costa Rica

Planta perennis, densicaespitosa. Radices graciles. Folia rigida, erecta, linearia, solum basalia, 1.5-8.0 dm longa, vaginis scaporum longiora; laminae vaginis 10-15-plo longiores, planae vel tortae, 2.5-4.5 mm latae, flavovirentae, valde compressae, longitudine leviter multinervosae, apices contracti, incurvato-acuti, incrassati, margines incrassati, persaepe papillosi; vaginae leviter carinatae, carinibus interdum ferrugineociliatis, lateribus glabris, brunneolis, nitidis, marginibus tenuibus integris vel basin versus ciliatis, in laminas gradatim convergentibus sed ad apicem ligulam triangulam 2.02.5 mm longam efferentes. Vaginae scaporum basin versus leviter compressae, laxae, brunneolae, nitidae; laminae breves, cuspidatae. Scapi lineares, recti, leviter torti, 5-7 dm alti, 1-2 mm lati, virides, apicem versus ancipiti, in sectione transversali elliptici, bicostati, costis papillosis. Spicae subcapitatae, pluriflorae, ca. 1 cm longae, 1 cm latae, bracteae ecarinatae, convexae, fuscae; bracteae steriles 6-7, ovatae, fertilibus breviores; bracteae fertiles laxe imbricatae, ovatae vel anguste ovatae, ca. 5 mm longae, integrae vel laceratae, tenues; area dorsali nulla. Sepala lateralia libera, fusca, inequilatera, leviter curvata, oblanceolata, ca. 5 mm longa, acuta; ala carinali firma, angusta, integra vel apicem versus ciliata. Laminae petalorum anguste obovatae, ca. 5 mm longae, apice rotundatae, erosae, cueatae, luteolae. Staminodia bibrachiata, brachiis apice sparsim longipenicillatis. Capsula ellipsoidea, 5 mm longa, placenta centralis. Semina oblonga, 0.8-1.0 mm longa, translucida, atroferruginea, 16-20-costata.

Root apical organization in monocotyledons—Xyridaceæ

The root apical organization of two species ofXyris has been investigated. The structural configuration shows discrete initials for plerome and rootcap and a common tier of initials for the epidermis and cortex. The cell complexes are analysed. The endodermis arises from an endodermis-periblem complex. Cyto-physiologically there is a quiescent centre to the tip of the root body with the real histogenetic zone, named the meristematic zone, surrounding it. The characteristics of these two zones are described.