The grass genera of the world

L. Watson, T.D. Macfarlane, and M.J. Dallwitz

Pheidochloa S. T. Blake

Habit, vegetative morphology. Slender annual; caespitose. Culms 20–50 cm high (filiform); herbaceous; branched above (P. vulpoides), or unbranched above. The branching simple. Culm nodes glabrous. Culm internodes solid. Plants unarmed. Young shoots intravaginal. Leaves non-auriculate. Leaf blades narrow; setaceous (short, convolute); without cross venation; persistent. Ligule a fringe of hairs.

Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets. The spikelets all alike in sexuality. Plants exposed-cleistogamous.

Inflorescence. Inflorescence few spikeleted (4–6); a single raceme, or paniculate (a raceme or depauperate panicle of few spikelets); espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes persistent. Spikelets not secund; pedicellate.

Female-fertile spikelets. Spikelets 6–13 mm long; compressed laterally; disarticulating above the glumes; with a distinctly elongated rachilla internode between the glumes (glabrous). Rachilla terminated by a female-fertile floret. Hairy callus present. Callus long; pointed.

Glumes present; two (separated by an unusually long internode); very unequal (G2 twice the length of G1); exceeding the spikelets; (the longer) long relative to the adjacent lemmas (much longer); hairless; pointed; awnless; carinate; similar (herbaceous-membranous). Lower glume 7 nerved. Upper glume 7 nerved. Spikelets with female-fertile florets only.

Female-fertile florets 2 (similar). Lemmas similar in texture to the glumes to decidedly firmer than the glumes; not becoming indurated (thinly cartilaginous, often purplish); entire; pointed; awned. Awns 1; median; apical; non-geniculate (purple); straight (bristle-like); about as long as the body of the lemma to much longer than the body of the lemma; entered by several veins (3 or 5). Lemmas hairy; non-carinate; without a germination flap; 7 nerved. Palea present (glabrous); relatively long; awnless, without apical setae; not indurated; 2-nerved; 2-keeled. Lodicules present; free; membranous (hyaline, minute); glabrous; not toothed. Stamens 2. Anthers minute; not penicillate; without an apically prolonged connective. Ovary apically glabrous. Styles free to their bases. Stigmas 2.

Fruit, embryo and seedling. Fruit free from both lemma and palea; small; linear; longitudinally grooved (concavo-convex); compressed dorsiventrally. Hilum long-linear. Embryo small; not waisted. Endosperm hard. Embryo without an epiblast; with a scutellar tail; with an elongated mesocotyl internode; with one scutellum bundle. Embryonic leaf margins meeting.

First seedling leaf with a well-developed lamina. The lamina fairly broad; curved.

Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Long-cells similar in shape costally and intercostally; of similar wall thickness costally and intercostally (fairly thick walled). Mid-intercostal long-cells rectangular, or fusiform (in the files containing the stomata); having markedly sinuous walls. Microhairs present; panicoid-type (the basal cell tending to be plump and distally inflated, the apical cell rather broad, but tapered and thin-walled); (42–)46–57(–58.5) microns long; (9–)9.6–14.4(–15) microns wide at the septum. Microhair total length/width at septum 3.6–6.3. Microhair apical cells (20.4–)27–33(–34.5) microns long. Microhair apical cell/total length ratio 0.48–0.63. Stomata common; (30–)33–36(–39) microns long. Subsidiaries triangular. Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells absent or very rare. Costal short-cells conspicuously in long rows. Costal silica bodies oryzoid and ‘panicoid-type’; mostly cross shaped (but many of the crosses more or less ‘oryzoid’, and most having points); sharp-pointed (many of the crosses are ‘oryzoid’ in form, and most have points).

Transverse section of leaf blade, physiology. C4; biochemical type NADP–ME (P. gracilis); XyMS+. PCR sheath outlines uneven. PCR sheath extensions absent. PCR cells without a suberised lamella. PCR cell chloroplasts ovoid; with well developed grana; centrifugal/peripheral. Mesophyll with radiate chlorenchyma. Leaf blade adaxially flat. Midrib not readily distinguishable; with one bundle only; with colourless mesophyll adaxially. Bulliforms not present in discrete, regular adaxial groups (epidermis of large cells, with no bulliform groups other than the small bulliforms-plus-colourless cells group over the median vascular bundle). All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders absent. Sclerenchyma all associated with vascular bundles.

Phytochemistry. Leaf blade chlorophyll a:b ratio 4.85–4.93.

Classification. Watson & Dallwitz (1994): Arundinoideae (or Panicoideae); Eriachneae. Soreng et al. (2015): Micrairoideae; Eriachneae. 2 species (P. gracilis, P. vulpioides).

Distribution, phytogeography, ecology. Australia & New Guinea.

In damp sandy heaths.

References, etc. Morphological/taxonomic: Blake 1944a. Leaf anatomical: studied by us - P. gracilis Blake, P. vulpioides Blake.

Illustrations. • P. vulpoides embryo in transverse section: this project. Pheidochloa vulpioides. • P. gracilis, abaxial epidermis of leaf blade: this project. • P. gracilis, abaxial epidermis of leaf blade: this project

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.’.