Andrea S. Vega

Structure and ultrastructure of leaf and calyx glands in Galphimia brasiliensis (Malpighiaceae).

The present study describes the anatomical structure of calyx and leaf glands in Galphimia brasiliensis and analyzes the mechanism of secretion. The glands are marginal and suprabasal, cup-shaped, sessile, and scarcely visible with the naked eye. Light microscopy reveals the following features: a thin, smooth cuticle; unistratified secretory cells; subglandular parenchyma; and vascular bundle supply composed of phloem and xylem with abundant druses of calcium oxalate. Transmission electron microscopy reveals the presence of secretory cells with conspicuous nuclei, dense cytoplasm, lipid droplets, numerous vesicles, mitochondria, Golgi, rough endoplasmic reticulum (RER), and elongated plastids with osmiophilic contents. The secretion reaches the apoplastic space and accumulates beneath the cuticle. Finally, the viscous, translucent exudate is eliminated by mechanical rupture of the cuticle. Histochemical analysis confirms that lipids are the main constituent. Small amounts of polysaccharides were also identified.

Occurrence and phylogenetic significance of latex in the Malpighiaceae

Latex and laticifers are reported for the first time in the genera Galphimia and Verrucularia (Malpighiaceae), with description and illustration of the leaf and stem anatomy of both genera. Those genera and the other two in which latex is known (Lophanthera and Spachea) constitute a single tribe, Galphimieae, that is at or near the base of the familys phylogeny, which suggests that latex in the Malpighiaceae may indicate an ancestor shared with the Euphorbiaceae.

Morphological interpretation of the spikelet in Digitaria atra (Poaceae: Panicoideae: Paniceae) and emended generic description

Digitaria atra is illustrated for the first time and the original description is emended. The diagnosis of the genus Digitaria is completed by introducing modifications related to the spikelets morphology and the lower lemmas consistency. Some remarks about the lower palea are included. The unusual morphological characteristics of the spikelet of D. atra are compared with the tribe Isachneae and some genera of Paniceae.

Elaiosomes in Urochloa paucispicata (Poaceae: Panicoideae: Paniceae): anatomy and chemical composition

Summary The spikelet of Urochloa paucispicata has a typical Paniceae structure and it constitutes the unit of dispersal; the base of its lower glume is united to an elongated internode between the lower and the upper glumes, and at maturity, it becomes soft and turgid, developing the elaiosome. Chemical identification of TLC fractions in the elaiosome of Urochloa paucispicata showed that it contains triglycerides, free fatty acids and diglycerides. Gas chromatography of the fatty acid methyl esters, of each fraction, showed the presence of palmitic, oleic, linoleic and stearic acids. Palmitic, oleic and linoleic acids are significant components of the lipid fractions. By field observations we identified three different species of ants (Hymenoptera: Formicidae) which removed the spikelets of Urochloa paucispicata and carried them to their nests: Acromyrmex landoltifracticomis FOREL, Pheidole spp. and Ectatomma spp.

Tripogon nicorae, a New Species and Synopsis of Tripogon (Poaceae: Chloridoideae) in America

Abstract Tripogon nicorae Rúgolo & A. S. Vega, a new species from South America, is described and illustrated. A key for the identification of Tripogon species in America is included and a comparative table based on morphology, leaf anatomy, micromorphological features of the spikelets, and ecology. The taxonomic synopsis includes synonymy, geographical distribution and ecology, iconography, vernacular names, and a list of representative specimens examined. Tripogon ekmanii Nicora & Rúgolo is reported for the first time in Uruguay.

A Morphology-Based Cladistic Analysis of Digitaria (Poaceae, Panicoideae, Paniceae)

Abstract A phylogenetic analysis was performed on 67 species of Digitaria belonging to four subgenera and 26 of the 32 sections recognized in Henrards monograph. The analysis was based on 113 discrete and six continuous morphological characters. In the resulting topologies the genus Digitaria was monophyletic. In spite of the low support for most groupings, several clades were recovered. The subdivision of Digitaria in the four subgenera proposed by Henrard was not supported since the large subgenus Digitaria appears as a paraphyletic assemblage within which the other three subgenera are nested. Nevertheless, the monophyly of some of Henrards sections was supported. This is the first approach to the phylogeny of Digitaria.

A New Species of Guadua (Poaceae, Bambusoideae, Bambuseae) and Synopsis of the Genus in Argentina and Neighboring Regions

Abstract A new species of Merostachys from the Bolivian Yungas, Merostachys yungasensis, is described and illustrated. Merostachys yungasensis is compared to other taxa distributed in Argentina, Bolivia, Paraguay, and Peru, in a table based on morphological characters. Additional micromorphological characters of foliage leaf blade and cauline epidermis are included. In Argentina two species are confirmed: M. claussenii and M. multiramea; the latter species constitutes a new report for this country and is excluded from Paraguay. The specific epithet of M. claussenii is emended, and a lectotype is here designated. Two new synonyms are recognized for M. claussenii and its presence is confirmed from Paraguay after an analysis of previous reports based on misidentifications. The taxa are illustrated. A key for the identification of the species, based on vegetative and reproductive characters, is also provided.

Digitaria killeenii (Poaceae: Panicoideae: Paniceae), a New Species from Bolivia

Abstract Digitaria killeenii A. S. Vega et Rúgolo, a new species from Bolivia, is described and illustrated. Additional micromorphological characters in the spikelets are also described. The presence of an apical, abaxial pair of stomata on the upper lemma and the presence of occasional brownish hairs on the lower palea constitute the first report in the genus Digitaria. The taxonomic position of D. killeenii is discussed and its inclusion in section Clavipilae (Stapf) Henrard is proposed. A comparative table and some remarks about the related taxa are included. Communicating Editor: Fred Barrie

LECTOTYPIFICATIONS IN TAXA OF THE GENERA CALAMAGROSTIS, DEYEUXIA, AND DIGITARIA (POACEAE)

Se designan aqui los lectotipos de 21 taxones pertenecientes a los generos Calamagrostis Adans., Deyeuxia Clarion ex P. Beauv. y Digitaria Haller emend. A. S. Vega & Rugolo sobre la base de especimenes y fragmentos obtenidos de material original depositado en los herbarios Berlin-Dahlem (B) y La Molina (MOL).

A New Species of Tarigidia (Poaceae, Panicoideae, Paniceae) from Puerto Rico and Additional Evidence for a Hybrid Origin of the Genus

Abstract A new species of Tarigidia from Puerto Rico is described and illustrated. Additional micromorphological characters of the inflorescence and spikelets are included. This species constitutes the first report of the genus Tarigidia in the New World. Tarigidia axelrodii grows together with Anthephora hermaphrodita and Digitaria bicornis, showing intermediate characters. This species gives additional evidence to support Loxtons hypothesis that Tarigidia is derived from hybridization between Anthephora and Digitaria and also supports the phylogenetic hypothesis showing close relationships between Anthephora and Digitaria.