Grass Genera of the World

L. Watson and M. J. Dallwitz


Pheidochloa S. T. Blake

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

Reproductive organization. Plants bisexual, 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; without proximal incomplete florets.

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 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.

Taxonomy. Arundinoideae (or Panicoideae); Eriachneae.

Distribution, ecology, phytogeography. 2 species; Australia & New Guinea. In damp sandy heaths.

Paleotropical and Australian. Indomalesian. Papuan. North and East Australian. Tropical North and East Australian.

References, etc. Morphological/taxonomic: Blake 1944a. Leaf anatomical: this project.

Illustrations. • Embryo, transverse section. Pheidochloa vulpioides. • Abaxial epidermis of leaf blade. Pheidochloa gracilis.


Cite this publication as: Watson, L., and Dallwitz, M. J. (1992 onwards). ‘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.’ http://biodiversity.uno.edu/delta/. Version: 18th August 1999. Dallwitz (1980), Dallwitz, Paine and Zurcher (1993 onwards, 1998), and Watson and Dallwitz (1994), and Watson, Dallwitz, and Johnston (1986) should also be cited (see References).

Index