Grass Genera of the World

L. Watson and M. J. Dallwitz


Hyperthelia W. Clayton

Sometimes referred to Hyparrhenia (including H. dissoluta)

Habit, vegetative morphology. Annual, or perennial; caespitose. Culms 100–750 cm high; herbaceous; to 1 cm in diameter; branched above (to form compound inflorescences). Culm nodes glabrous. Culm sheaths persistent. Culm internodes hollow. Young shoots intravaginal. The shoots not aromatic. Leaves not basally aggregated; non-auriculate. Leaf blades linear; broad, or narrow; 3–40 mm wide; flat, or rolled (on drying); pseudopetiolate (pseudopetioles to 16 cm long), or not pseudopetiolate; without cross venation; persistent; an unfringed membrane (usually), or a fringed membrane (rarely); truncate, or not truncate (rounded to acute, the upper edges of the sheath adnate to its sides); 3–4 mm long. Contra-ligule absent.

Reproductive organization. Plants bisexual, with bisexual spikelets; with hermaphrodite florets. The spikelets of sexually distinct forms on the same plant; hermaphrodite and male-only. The male and female-fertile spikelets mixed in the inflorescence. The spikelets overtly heteromorphic; in both homogamous and heterogamous combinations (with one homogamous pair, at the base of the lower raceme).

Inflorescence. Inflorescence falsely paniculate (large, leafy); spatheate; a complex of ‘partial inflorescences’ and intervening foliar organs. Spikelet-bearing axes very much reduced (usually), or ‘racemes’ (rarely); the spikelet-bearing axes usually with only one spikelet-bearing ‘article’ (rarely with 4 or 5); spikelet-bearing axes paired (the pair subtended by a linear to lanceolate spatheole, the bases terete, sometimes deflexed); with very slender rachides; disarticulating; disarticulating at the joints. ‘Articles’ linear; appendaged (the raceme-base with a long scarious appendage at the tip, 3–20 mm long, flat or rolled into a funnel around the raceme base); disarticulating obliquely. Spikelets paired, or in triplets (sometimes having one female-fertile spikelet with a pair of pedicelled male spikelets, the triplet disarticulating in its entirety); consistently in ‘long-and-short’ combinations; in pedicellate/sessile combinations. Pedicels of the ‘pedicellate’ spikelets free of the rachis. The ‘shorter’ spikelets hermaphrodite (in the heterogamous combinations), or male-only (in the homogamous combinations). The ‘longer’ spikelets male-only.

Female-sterile spikelets. The homogamous and pedicellate spikelets male, linear-lanceolate, with two hyaline lemmas; pedicellate spikelets with a short basal callus. The male spikelets 2 floreted.

Female-fertile spikelets. Spikelets 8–35 mm long; abaxial; not noticeably compressed to compressed dorsiventrally; biconvex; falling with the glumes; not disarticulating between the florets; with conventional internode spacings. Rachilla terminated by a female-fertile floret. Hairy callus present. Callus long; pointed.

Glumes two; more or less equal; exceeding the spikelets; long relative to the adjacent lemmas; dorsiventral to the rachis; hairy (G1, towards the tip), or hairless (G2); without conspicuous tufts or rows of hairs; not pointed (G1 bifurcate, G2 blunt); awned (G2, sometimes), or awnless; non-carinate; very dissimilar. Lower glume much exceeding the lowest lemma; not two-keeled; sulcate on the back; not pitted; relatively smooth. Upper glume 1 nerved. Spikelets with incomplete florets. The incomplete florets proximal to the female-fertile florets. Spikelets with proximal incomplete florets. The proximal incomplete florets 1; epaleate; sterile. The proximal lemmas awnless; 0 nerved; similar in texture to the female-fertile lemmas (hyaline); not becoming indurated.

Female-fertile florets 1. Lemmas less firm than the glumes (hyaline at margins and tips); becoming indurated along a central sulcate column below the awn; incised; shortly 2 lobed; not deeply cleft; awned. Awns 1; median; from a sinus; geniculate; hairy; much longer than the body of the lemma. Lemmas hairless (or with a few hairs only, at the edges); non-carinate (flat, sulcate); without a germination flap; 1 nerved. Palea present, or absent; when present, conspicuous but relatively short, or very reduced. Lodicules present; 2; free; fleshy; glabrous. Stamens 3. Anthers 3–4 mm long; not penicillate; without an apically prolonged connective. Ovary glabrous. Styles free to their bases. Stigmas 2; dark red pigmented.

Fruit, embryo and seedling. Fruit free from both lemma and palea; narrowly ellipsoid. Hilum short. Embryo large.

Abaxial leaf blade epidermis. Stomata common. Subsidiaries dome-shaped and triangular. Intercostal short-cells absent or very rare. Costal short-cells conspicuously in long rows. Costal silica bodies ‘panicoid-type’.

Transverse section of leaf blade, physiology. C4; XyMS–. PCR cell chloroplasts centrifugal/peripheral. Mesophyll without adaxial palisade. Leaf blade adaxially flat (practically smooth). Midrib conspicuous; having complex vascularization. Bulliforms somtimes present in discrete, regular adaxial groups (but mostly in irregular groups); sometimes in simple fans. Many of the smallest vascular bundles unaccompanied by sclerenchyma. Combined sclerenchyma girders present (with most large bundles).

Special diagnostic feature. Spikelets in much-reduced andropogonoid ‘racemes’, each of the latter reduced to a single triplet and enclosed at its base by a trumpet-like development of the peduncle tip (sometimes), or not borne as in ‘Anadelphia scyphofera’ (q.v.).

Cytology. Chromosome base number, x = 10.

Taxonomy. Panicoideae; Andropogonodae; Andropogoneae; Andropogoninae.

Distribution, ecology, phytogeography. 6 species; tropical and southern Africa. Mesophytic; species of open habitats; glycophytic. Grasslands and savanna.

Paleotropical. African and Madagascan. Sudano-Angolan, West African Rainforest, and Namib-Karoo. Sahelo-Sudanian, Somalo-Ethiopian, South Tropical African, and Kalaharian.

Economic importance. Grain crop species: Hyperthelia edulis harvested wild.

References, etc. Morphological/taxonomic: Clayton 1966. Leaf anatomical: this project.

Illustrations. • General aspect


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