The grass genera of the world
Type species: Type: A. repens B.K.Simon.
Habit, vegetative morphology. Perennial; stoloniferous. Culms 18–24 cm high; herbaceous; not scandent; sparingly branched above; 3–4 noded. Culm nodes hidden by leaf sheaths. Culm leaf sheaths compressed. Plants unarmed; without multicellular glands. The shoots not aromatic. Leaves not basally aggregated; non-auriculate; without auricular setae. Sheath margins free. The sheaths keeled. Leaf blades linear; broad; 1–2 mm wide; flat to folded; not needle-like; without cross venation; persistent. Ligule a fringe of hairs.
Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets. The spikelets hermaphrodite. Plants without hidden cleistogenes.
Inflorescence. Inflorescence few spikeleted; depauperate, a single raceme, or paniculate. Primary inflorescence branches inserted all around the main axis. Inflorescence with axes ending in spikelets. Inflorescence espatheate; not comprising partial inflorescences and foliar organs. The racemes spikelet bearing to the base. Spikelets unaccompanied by bractiform involucres, not associated with setiform vestigial branches; solitary; long pedicellate (the pedicels 4–7 mm long). Pedicel apices cupuliform. Spikelets not imbricate.
Female-fertile spikelets. Spikelets 3–3.5 mm long; lanceolate to ovate; adaxial; compressed laterally; falling with the glumes; with conventional internode spacings. The upper floret not stipitate. Rachilla terminated by a female-fertile floret. Hairy callus absent.
Glumes two; very unequal (the upper longer); (the upper) shorter than the spikelets to about equalling the spikelets; (the upper) shorter than the adjacent lemmas to long relative to the adjacent lemmas; scantily hairy (the upper, with a few cushion based hairs), or hairless (the lower); pointed; awnless; non-carinate; similar (papery, ovate to elliptic). Lower glume about 0.75 times the length of the upper glume; much shorter than the lowest lemma; longer than half length of lowest lemma; 5 nerved, or 7 nerved. Upper glume not saccate; 9 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. Palea of the proximal incomplete florets fully developed; not becoming conspicuously hardened and enlarged laterally. The proximal incomplete florets male. The proximal lemmas similar to the upper glume; awnless; 9 nerved; decidedly exceeding the female-fertile lemmas; less firm than the female-fertile lemmas to similar in texture to the female-fertile lemmas (papery); not becoming indurated.
Female-fertile florets 1. Lemmas not saccate; firmly membranous or thinly cartilaginous; striate; not becoming indurated (no more than very thinly cartilaginous); yellow in fruit; entire; pointed (acute); not crested; awnless; hairless; non-carinate; having the margins lying flat on the palea; probably with a clear germination flap (the material seen disintegrating, but hinting at one); obscurely 5 nerved. Palea present; relatively long; gaping; entire; awnless, without apical setae; textured like the lemma; not indurated; 2-nerved; keel-less. Lodicules present; 2; free; membranous (quite large); ciliate; not or scarcely vascularized. Stamens 3. Anthers 0.8 mm long.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Long-cells markedly different in shape costally and intercostally (the costals much narrower); of similar wall thickness costally and intercostally (thin walled). Mid-intercostal long-cells rectangular; having markedly sinuous walls. Microhairs present; elongated; clearly two-celled; panicoid-type; about 70 microns long; about 15 microns wide at the septum. Microhair total length/width at septum 3–6. Microhair apical cells about 50 microns long. Microhair apical cell/total length ratio 0.7–0.8. Stomata common; about 40 microns long. Subsidiaries non-papillate; parallel-sided, dome-shaped, and triangular (low to medium, predominantly more or less triangular with the apices truncated to various extents); including both triangular and parallel-sided forms on the same leaf. Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells absent or very rare. Macrohairs infrequent, intergrading with long prickles, 1–2(-3) celled. Costal short-cells conspicuously in long rows. Costal silica bodies present and well developed; panicoid-type; consistently elongated nodular.
Transverse section of leaf blade, physiology. C4; XyMS. PCR sheath outlines uneven. PCR sheath extensions absent. Mesophyll without circular cells. Leaf blade adaxially flat. Midrib conspicuous (by virtue of a conspicuous abaxial keel, an arc of enlarged adaxial epidermal cells and some colourless mesophyll); with one bundle only, or having complex vascularization (depending on interpretation of the minor bundles flanking the median); with colourless mesophyll adaxially (in the form of a few large cells contigous with the bulliform epidermis). The lamina symmetrical on either side of the midrib. Bulliforms not present in discrete, regular adaxial groups (the adaxial epidermis mainly bulliform). Many of the smallest vascular bundles unaccompanied by sclerenchyma. Combined sclerenchyma girders absent (the sclerenchyma restricted to a large abaxial strand in the keel, and small adaxial and abaxial strands with the major laterals). Sclerenchyma all associated with vascular bundles.
Classification. Watson & Dallwitz (1994): Panicoideae; Panicodae; Paniceae. Soreng et al. (2015): Panicoideae; Panicodae; Paniceae; Cenchrinae. 1 species (A. repens).
Distribution, phytogeography, ecology. New South Wales.
Mesophytic; halophytic to glycophytic.
References, etc. Morphological/taxonomic: B.K. Simon 1992. Leaf anatomical: studied by us.
Special comments. Fruit data wanting. Illustrations. • A. repens, general aspect and spikelet: Simon, 1992. • A. repens, abaxial epidermis of leaf blade, microhair: this project. • A. repensm transverse section of leaf blade: this project. Alexfloydia repens. Midrib and adjoining.
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: 11th December 2017. delta-intkey.com/grass’.