Chrysochloa Swallen
Including Bracteola Swallen
Habit, vegetative morphology. Annual, or perennial; stoloniferous, or caespitose. The flowering culms leafy. Culms 10–75 cm high; herbaceous. Culm nodes glabrous. Culm internodes solid. Plants unarmed. Young shoots intravaginal. Leaves mostly basal; non-auriculate. Leaf blades narrow; 3–6 mm wide (strap-shaped, the apices blunt); not setaceous (flat, folded or enrolled); without abaxial multicellular glands; without cross venation; persistent; a fringed membrane; truncate. Contra-ligule absent.
Reproductive organization. Plants bisexual, with bisexual spikelets; with hermaphrodite florets. The spikelets all alike in sexuality (save that terminal spikelets may be reduced).
Inflorescence. Inflorescence of spicate main branches; digitate, or subdigitate (a terminal, spreading-ascending verticil of racemes). Primary inflorescence branches 2–6. Rachides trigonous. Inflorescence espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes spikelike; persistent. Spikelets solitary; secund; narrowly biseriate; subsessile (appressed); imbricate; not in distinct ‘long-and-short’ combinations.
Female-fertile spikelets. Spikelets 3–5 mm long; strongly compressed laterally; disarticulating between the glumes (leaving G1 on the rachis); disarticulating between the florets; with conventional internode spacings. Rachilla prolonged beyond the uppermost female-fertile floret; hairless; the rachilla extension with incomplete florets. Hairy callus absent.
Glumes two; more or less equal; long relative to the adjacent lemmas; hairless; pointed; shortly awned (G2 sometimes), or awnless; carinate (and G1 laterally compressed), or carinate and non-carinate (G2 sometimes rounded on back); narrow, lanceolate, membranous. Lower glume 1 nerved. Upper glume 1 nerved, or 5 nerved (C. orientalis). Spikelets with incomplete florets. The incomplete florets distal to the female-fertile florets. The distal incomplete florets 1 (male or sterile); merely underdeveloped. Spikelets without proximal incomplete florets.
Female-fertile florets 1. Lemmas similar in texture to the glumes to decidedly firmer than the glumes (firmly membranous to leathery); not becoming indurated; entire; pointed; mucronate, or awned. Awns when present, 1; dorsal; from near the top (subapical); non-geniculate; straight, or flexuous; hairless (glabrous or scabrid); much shorter than the body of the lemma. Lemmas hairy (villous on the nerves); carinate; without a germination flap; 3 nerved. Palea present; relatively long; apically notched; awnless, without apical setae; thinner than the lemma; not indurated (very thin); 2-nerved; 2-keeled. Lodicules present; 2; free; fleshy; glabrous; not or scarcely vascularized. Stamens 3. Anthers not penicillate (relatively long); 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 (but embraced); ellipsoid; trigonous. Pericarp fused.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae present; intercostal. Intercostal papillae over-arching the stomata (slightly); consisting of one symmetrical projection per cell (one thick-walled papilla in the middle of each intercostal cell). Long-cells markedly different in shape costally and intercostally (costals normal); of similar wall thickness costally and intercostally (thick walled). Intercostal zones exhibiting many atypical long-cells (the ‘long-cells’ and interstomatals short). Mid-intercostal long-cells rectangular; having markedly sinuous walls. Microhairs present; more or less spherical (about 9µ in diameter); ostensibly one-celled; chloridoid-type; about 9 microns long. Stomata common; 18–21 microns long. Subsidiaries non-papillate; predominantly triangular. Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells common; not paired (solitary); silicified. Intercostal silica bodies absent; small. Costal short-cells conspicuously in long rows. Costal silica bodies present in alternate cell files of the costal zones; exclusively saddle shaped.
Transverse section of leaf blade, physiology. Lamina mid-zone in transverse section open.
C4; XyMS+. PCR sheaths of the primary vascular bundles interrupted; interrupted both abaxially and adaxially. PCR sheath extensions absent. Leaf blade adaxially flat. Midrib conspicuous (via a large, narrow abaxial keel); having a conventional arc of bundles (a large median and a smaller lateral on either side); with colourless mesophyll adaxially (midrib and adjoining lamina adaxially colourless). Bulliforms present in discrete, regular adaxial groups (between all the lamina bundles); associated with colourless mesophyll cells to form deeply-penetrating fans (the fans large, rather irregularly shaped). All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present (with all the bundles); forming ‘figures’ (most bundles with scanty girders; submarginal bundles with heavy I-shaped combinations). Sclerenchyma all associated with vascular bundles.
Cytology. 2n = 14.
Taxonomy. Chloridoideae; main chloridoid assemblage.
Distribution, ecology, phytogeography. 5 species; tropical Africa. Species of open habitats. Seasonally waterlogged ground.
Paleotropical. African. Sudano-Angolan and West African Rainforest. Sahelo-Sudanian, Somalo-Ethiopian, and South Tropical African.
References, etc. Leaf anatomical: this project.
Illustrations. • Abaxial epidermis of leaf blade. • Abaxial epidermis of leaf blade
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).
