| # The grass genera of the world |

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

### Phanopyrum Raf.

~ Panicum gymnocarpon

Type species: P. gymnocarpon (Ell.) Nash.

Habit, vegetative morphology. Succulent, glabrous perennial; stoloniferous and decumbent (the stolons to 2 m long). Culms 60–130 cm high; thick, decumbent, succulent, rooting profusely at the lower nodes; not tuberous. Culm nodes glabrous. Leaf blades linear-lanceolate (tapering from midlength); broad; blades 15–40 cm long, 7–25 mm wide; flat. Ligule an unfringed membrane (?); 0.5–1.5 mm long.

Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets. The spikelets hermaphrodite.

Inflorescence. Inflorescence 20–40 cm long, of spicate main branches, or paniculate (the spikelike branches ascending); open; non-digitate. Primary inflorescence branches inserted all around the main axis (whorled). Inflorescence espatheate. Spikelets secund (on the ultimate branchlets); in secund clusters, shortly pedicellate, or sessile to subsessile.

Female-fertile spikelets. Spikelets 6–7 mm long; lanceolate; compressed laterally; falling with the glumes; with distinctly elongated rachilla internodes between the florets. The upper floret conspicuously stipitate. Rachilla terminated by a female-fertile floret. Hairy callus absent.

Glumes two; spreading at maturity, very unequal to more or less equal (the lower somewhat shorter); (at least the upper) exceeding the spikelets; long relative to the adjacent lemmas; hairless; glabrous; acuminate- pointed; awnless; similar. Lower glume about 0.7–0.9 times the length of the upper glume; about equalling the lowest lemma (nearly as long); much longer than half length of lowest lemma (almost equalling it); 3 nerved. Upper glume 3 nerved. Spikelets with incomplete florets. The incomplete florets proximal to the female-fertile florets. Spikelets with proximal incomplete florets. The proximal incomplete florets 1; paleate. Palea of the proximal incomplete florets reduced (small, thin, lanceolate). The proximal incomplete florets sterile. The proximal lemmas awnless; 3 nerved; more or less equalling the female-fertile lemmas, or decidedly exceeding the female-fertile lemmas (?); not becoming indurated.

Female-fertile florets 1. Lemmas decidedly firmer than the glumes; shining, smooth; short, stipitate, becoming indurated (only 2 mm long); lustrous, pale to brownish; entire; awnless; hairless; non-carinate; having the margins inrolled against the palea. Palea present.

Transverse section of leaf blade, physiology. C3.

Cytology. Chromosome base number, x = 10. 2n = 40.

Classification. Watson & Dallwitz (1994): genus not recognised. Soreng et al. (2015): Panicoideae; Panicodae; Paspaleae; Arthropogoninae. 1 species (P. gymnocarpon (Ell.) Nash).

Distribution, phytogeography, ecology. Restricted to the U.S.A.

Holarctic.

Hydrophytic to helophytic; shade species; glycophytic. In swamps, wet woodlands, and the marshy shores of lakes and streams; also occasionally in shallow water, often in the shade.

References, etc. Morphological/taxonomic: Hitchcock & Chase (1950).

Special comments. Fruit data wanting. Anatomical data wanting.

Illustrations. • Phaneropyrum gymnocarpon: as Panicum, Hitchcock and Chase (1950).

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: 15th June 2025. delta-intkey.com’.

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