Resumen Se describe e ilustra la especie Moutabea chartacea, de los bosques húmedos de tierras bajas de Brasil (estado Amazonas), Venezuela (estados Amazonas, Bolívar y Delta Amacuro) y Colombia (departamentos de Caquetá, Meta y Vaupés), y se discuten sus relaciones morfológicas con su especie afín. Esta nueva especie es similar a M. gentryi, sin embargo, difiere por poseer los pecíolos, hojas, lóbulos de cáliz, frutos y semillas más pequeños, así como brácteas triangulares, pétalos con los ápices no reflexos y semillas densamente cubiertas por tricomas estrellados. Se incluye una clave actualizada de las especies de Moutabea.

Abstract We describe and illustrate Moutabea chartacea from the wet lowland forests of Brazil (Amazonas state), Venezuela (Amazonas, Bolívar and Delta Amacuro states), and Colombia (Caquetá, Meta and Vaupés departments), and we discuss its morphological relationships with an allied species. This new species is similar to M. gentryi, but it differs by its smaller petioles, leaf blades, calyx lobes, fruit, and seeds; triangular bracts; petals not reflexed; and the seed densely covered by stellate trichomes. An updated key to the named species of Moutabea is provided.

Abstract A taxonomic treatment of the Xyridaceae in the Viruá National Park is presented. Located in Roraima state, northern Brazil, the park comprises a mosaic of lowland vegetation types, including forests, wetlands, and one of the largest continuous areas of campinarana in the Brazilian Amazon Basin. Xyridaceae are represented in the park by 20 species in the genera Abolboda and Xyris. Although the four species of Abolboda are widespread, most of the Xyris species (75%) are endemic to Amazonian open vegetation formations, such as campinaranas and savannas. This study was based on field, herbarium, and scanning electron microscopy research. The taxonomic treatment includes identification keys to the genera and species, morphological descriptions, SEM images of seeds for Xyris species, iconography, geographic distribution and comments on the ecology of the species. The poorly known Xyris connosepala is synonymized in Xyris guianensis.

RESUMO Caraipa andina foi descoberta em La Fundación, nos Andes Ocidentais da Venezuela (Estado de Táchira) e é aqui descrita e ilustrada, discutindo-se suas afinidades morfológicas com as espécies próximas. Morfologicamente relacionada com C. heterocarpa Ducke, a nova espécie diferencia-se pelo tamanho, forma da lâmina foliar e face abaxial densamente papilosa; inflorescência paucifloras; pedicelos, botões florais, pétalas e filamentos mais curtos. Informações sobre a fitogeografia do local são apresentadas. Esta espécie representa o primeiro registro deste gênero nos Andes Venezuelanos.

ABSTRACT Caraipa andina from La Fundación, in the western Andes of Venezuela (Táchira State) is described, illustrated, and its morphological relationship with an allied species is discussed. This new species is morphologically related to C. heterocarpa Ducke, but it differs by the leaf blade shape, size, and dense abaxial papillae; fewerflowered inflorescence; and shorter pedicel, flower buds, petals, and filaments. Phytogeographical information about the La Fundación area is presented. This species represents the first report of this genus in the Venezuelan Andes.

El centro de mayor diversidad genérica de la familia Xyridaceae se encuentra al norte de América del Sur, donde se han detectado cuatro géneros endémicos de los cinco reconocidos en la familia. Muchos taxones representativos de estos géneros endémicos tienen una distribución geográfica restringida y no se han estudiado críticamente, incluyendo la única especie del género Aratitiyopea. Poblaciones de esta Xyridaceae extraordinaria se encuentran a elevaciones medias en bosques montañosos. La mayoría de las Xyridaceae se encuentran en ambientes expuestos, oligotróficos y que a pesar de ser al menos estacionalmente húmedos, muchas especies muestran adaptaciones xeromórficas. En contraste, Aratitiyopea presenta características morfológicas y de anatomía interna particulares de un mesófito (tallos rastreros, hojas con una lámina relativamente ancha, poco tejido mecánico y la falta de una hipodermis presente en otras Xyridaceae con hojas bifaciales) así como efectos de resecamiento estacional (muerte de células en la raíz y engrosamiento de las paredes celulares endodermales). En este trabajo se presentan estudios morfológicos y anatómicos de las partes vegetativas de Aratitiyopea y se comparan con estudios previos de otros miembros de las Xyridaceae. Aunque el aspecto general de Aratitiyopea es aberrante en Xyridaceae, el género es estructuralmente consistente con la familia, y los caracteres poco usuales son interpretados como adaptaciones a su ambiente típico que comparte con muy pocas otras Xyridaceae.

The center of generic diversity of the monocot family Xyridaceae is northern South America, where four of the five genera are endemic. Many species of these four small genera have restricted distributions and have not been critically studied, including the monospecific genus Aratitiyopea. Populations of this unusual Xyridaceae occur in mid-elevation, forested montane sites. Most Xyridaceae occur in exposed habitats, and although they are at least seasonally wet, many species exhibit xeromorphic adaptations. In contrast, Aratitiyopea presents a morphology and internal anatomy of a mesophyte (trailing stems, leaves with a relatively broad lamina, little mechanical tissue, and lacking a hypodermis, the latter two features present in other Xyridaceae with bifacial leaves) as well as effects of seasonal drying (cell death in the root and thickened endodermal cell walls). Structural details of the vegetative body of Aratitiyopea are presented here, and compared to that known for other Xyridaceae. Although the "gestalt" of Aratitiyopea is aberrant in Xyridaceae, it is structurally consistent with the family, and unusual features are interpreted as adaptations to its habitat, which few other Xyridaceae occupy.