The grass genera of the world
Habit, vegetative morphology. Perennial; caespitose (?). Culms 30–80 cm high; branched above to unbranched above. Culm internodes hollow. Leaves non-auriculate; without auricular setae. Leaf blades linear, or linear-lanceolate, or lanceolate; not pseudopetiolate. Ligule a fringe of hairs.
Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets. The spikelets hermaphrodite.
Inflorescence. Inflorescence paniculate; open to contracted. Primary inflorescence branches inserted all around the main axis. Inflorescence espatheate; not comprising partial inflorescences and foliar organs. Spikelets solitary, or paired; pedicellate. Pedicel apices discoid. Spikelets not in distinct long-and-short combinations.
Female-fertile spikelets. Spikelets morphologically conventional (A. scabrum), or unconventional (A. chapadense); 3.4–7.2 mm long; oblong, or lanceolate; compressed dorsiventrally; falling with the glumes; with conventional internode spacings. Rachilla terminated by a female-fertile floret. Hairy callus present.
Glumes one per spikelet (A. chapadense), or two (A. scabrum); when both present, more or less equal, or very unequal to more or less equal; long relative to the adjacent lemmas (i.e., the upper); when present subulate (i.e., the upper one, in A. scabrum); awned (the upper, the lower if present subulate); non-carinate; very dissimilar (the lower if present subulate, the upper oblong). Lower glume shorter than the lowest lemma. Upper glume 3–5 nerved. Spikelets with incomplete florets. The incomplete florets proximal to the female-fertile florets. Spikelets with proximal incomplete florets. The proximal incomplete florets 1; paleate (sometimes, in A. scabrum), or epaleate; sterile (no floret). The proximal lemmas oblong; awnless (the apex entire); 3 nerved; decidedly exceeding the female-fertile lemmas; similar in texture to the upper glume; not becoming indurated.
Female-fertile florets 1. Lemmas when present, short and linear, absent in A. chapadense; when present, less firm than the glumes; not becoming indurated (membranous, in A. scabrum); blunt. Palea absent (A. chapadense), or present to absent (A. scabrum); if present, very reduced. Lodicules present; 2; fleshy. Stamens 3. Ovary apically glabrous. Stigmas 2.
Fruit, embryo and seedling. Disseminule a free caryopsis. Fruit not grooved; compressed dorsiventrally; smooth. Hilum short. Pericarp fused. Embryo rather large (about a third the length of the caryopsis).
Abaxial leaf blade epidermis. Microhairs present; panicoid-type. Microhair apical cell wall thinner than that of the basal cell and often collapsed.
Transverse section of leaf blade, physiology. C4. The anatomical organization unconventional. Organization of PCR tissue Arundinella type. XyMS. Leaf blade with distinct, prominent adaxial ribs to adaxially flat. Midrib not readily distinguishable; with one bundle only. Bulliforms present in discrete, regular adaxial groups; in simple fans. Combined sclerenchyma girders present; forming figures. Sclerenchyma all associated with vascular bundles.
Classification. Watson & Dallwitz (1994): not described separately. Soreng et al. (2015): Panicoideae; Panicodae; Paspaleae; Arthropogoninae. 2 species.
Distribution, phytogeography, ecology. Brazil, Bolivia.
References, etc. Morphological/taxonomic: Filigueiras et al. (2001), confusion over lower glume of A. chapadense (cf. illustration and key). Leaf anatomical: Filigueiras et al. (2001), with leaf epidermal data restricted to S.E.M.
Special comments. Anatomical data for ts only. Illustrations. • A. chapadense: Filigueiras et al., Ann. Miss. Bot. Gard. 88 (2001). • A. scaber: Filigueiras et al., Ann. Miss. Bot. Gard. 88 (2001)
We advise against extracting comparative information from the descriptions. This is much more easily achieved using the DELTA data files or the interactive key, which allows access to the character list, illustrations, full and partial descriptions, diagnostic descriptions, differences and similarities between taxa, lists of taxa exhibiting or lacking specified attributes, distributions of character states within any set of taxa, geographical distribution, and classifications. See also Guidelines for using data taken from Web publications.
Cite this publication as: ‘Watson, L., Macfarlane, T.D., and Dallwitz, M.J. 1992 onwards. The grass genera of the world: descriptions, illustrations, identification, and information retrieval; including synonyms, morphology, anatomy, physiology, phytochemistry, cytology, classification, pathogens, world and local distribution, and references. Version: 13th November 2017. delta-intkey.com/grass’.