Prosphytochloa Schweickerdt
Sometimes referred to Potamophila (P. prehensilis)
Habit, vegetative morphology. Perennial; rhizomatous (the rhizomes horizontal, with cataphylls). The flowering culms leafy. Culms 1000 cm high (or more); herbaceous; scandent (by retrorse hairs on the leaf blade margins); branched above. Culm nodes hairy, or glabrous. Culm internodes hollow. Plants unarmed (but leaf margins and main veins spiny, with minute retrorse barbs). Young shoots intravaginal. Leaves not basally aggregated; auriculate (sheaths slightly auricled); without auricular setae. Leaf blades linear-lanceolate to lanceolate; narrow to broad; 4–15 mm wide; flat; without cross venation; persistent; rolled in bud; an unfringed membrane; not truncate (rounded, the margin lacerate-fimbriate); 1–1.5 mm long. Contra-ligule absent.
Reproductive organization. Plants bisexual, with bisexual spikelets; with hermaphrodite florets.
Inflorescence. Inflorescence paniculate (terminating main culm and laterals, the branchlets fine and stiff); open; espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes persistent. Spikelets solitary; not secund; pedicellate.
Female-fertile spikelets. Spikelets unconventional (by virtue of the reduced glumes); 6–9 mm long; slightly compressed laterally; disarticulating above the glumes (i.e. above the rudimentary glumes); not disarticulating between the florets. Rachilla terminated by a female-fertile floret. Hairy callus absent. Callus absent.
Glumes present, or absent; two (reduced to a bilobed to entire hyaline cup); minute; more or less equal; shorter than the spikelets; shorter than the adjacent lemmas; joined; hairless; glabrous; not pointed (blunt); awnless. Lower glume 0 nerved. Upper glume 0 nerved. Spikelets with incomplete florets. The incomplete florets proximal to the female-fertile florets. The proximal incomplete florets 2; epaleate; sterile (subulate, edged with minute hyaline spines, variable in size). The proximal lemmas awnless; 1 nerved; exceeded by the female-fertile lemmas (very short).
Female-fertile florets 1. Lemmas acuminate; chartaceous or leathery; entire; pointed; awnless; hairless; scabrous; carinate (the nerves with prickles); without a germination flap; 5 nerved; with the nerves confluent towards the tip. Palea present (similar to the lemma, which clasps it); relatively long; tightly clasped by the lemma; entire (acuminate); awnless, without apical setae; textured like the lemma; leathery; several nerved (3); one-keeled. Lodicules present; 2; free; membranous (above, but fleshy below); glabrous; not toothed; heavily vascularized. Stamens 6. Anthers 5 mm long; not penicillate; without an apically prolonged connective. Ovary glabrous. Styles free to their bases. Stigmas 2 (plumose); white.
Fruit, embryo and seedling. Fruit free from both lemma and palea; medium sized (5 to 6 mm long, brown); fusiform; longitudinally grooved; not noticeably compressed; longitudinally ribbed. Hilum long-linear. Embryo small. Endosperm containing compound starch grains. Embryo with an epiblast; without a scutellar tail.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae present. Intercostal papillae several per cell (one or two rows of small, circular papillae on each long-cell, and the guard-cells overtopped by four small papillae, two from each subsidiary). Long-cells markedly different in shape costally and intercostally (the costals relatively long and narrow); of similar wall thickness costally and intercostally (walls of medium thickness). Mid-intercostal long-cells rectangular; having markedly sinuous walls. Microhairs present; panicoid-type; 45–48 microns long; 5.4–6 microns wide at the septum. Microhair total length/width at septum 7.5–8.9. Microhair apical cells (19.5–)21–22(–22.5) microns long. Microhair apical cell/total length ratio 0.41–0.49. Stomata common; 21–22.5 microns long. Subsidiaries papillate; dome-shaped to triangular. Guard-cells overlapped by the interstomatals (slightly). Intercostal short-cells absent or very rare. Costal short-cells conspicuously in long rows. Costal silica bodies oryzoid; not sharp-pointed.
Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll with non-radiate chlorenchyma; without adaxial palisade; with arm cells; with fusoids (i.e. with lateral sheath extensions), or without fusoids (if these not so interpreted). The fusoids an integral part of the PBS. Leaf blade adaxially flat. Midrib conspicuous; having complex vascularization (there being a small bundle adaxial to the main one); with colourless mesophyll adaxially. The lamina symmetrical on either side of the midrib. Bulliforms present in discrete, regular adaxial groups; in simple fans (the fans broad). All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present; forming ‘figures’. Sclerenchyma all associated with vascular bundles.
Special diagnostic feature. Scandent via leaf blades with retrorsely scabrid margins.
Cytology. Chromosome base number, x = 12. 2n = 24. 2 ploid.
Taxonomy. Bambusoideae; Oryzodae; Oryzeae.
Distribution, ecology, phytogeography. 1 species; South Africa. Helophytic; shade species; glycophytic.
Paleotropical. African. Sudano-Angolan. South Tropical African.
References, etc. Morphological/taxonomic: de Winter 1951. 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).
