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The grass genera of the world

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

Dichanthelium (A. Hitchc. & Chase) Gould

~ Panicum

Including Adenochloa Zuloaga, Parodiophyllochloa

Habit, vegetative morphology. Perennial (with a rosette of short winter leaves); from a crown or with short matted rhizomes. Culms 20–70(–150) cm high; herbaceous. Culm internodes solid, or hollow. Plants with multicellular glands (Adenochloa), or without multicellular glands. Leaves non-auriculate. Leaf blades broad, or narrow; usually flat; rolled in bud. Ligule an unfringed membrane to a fringe of hairs (?).

Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets. The spikelets of sexually distinct forms on the same plant (the first-formed spikelets rarely perfecting seed save in the Lanuginosa group and D. clandestinum; secondary branches from the primary panicle bearing cleistogamous, fertile spikelets); hermaphrodite, or hermaphrodite and sterile. Plants exposed-cleistogamous, or chasmogamous; with hidden cleistogenes (often), or without hidden cleistogenes. The hidden cleistogenes in the leaf sheaths. Apomictic, or reproducing sexually.

Inflorescence. Inflorescence paniculate (primarily a terminal open panicle, with chasmogamous or abortive spikelets, subsequently complicated by branching from the culm nodes and production of secondary inflorescences); open; with capillary branchlets (often flexuous), or without capillary branchlets; ultimately a complex of ‘partial inflorescences’ and intervening foliar organs (the secondary branches repeatedly branching, the short branchlets fascicled and with very reduced leaves). Spikelet-bearing axes very much reduced (the grain bearing, cleistogamous ones), or paniculate; the terminal branches of the primary culm often falling. Spikelets not secund; pedicellate.

Female-fertile spikelets. Spikelets cleistogamous; 1.4–4.3 mm long; compressed dorsiventrally; falling with the glumes; with conventional internode spacings, or with distinctly elongated rachilla internodes between the florets. The upper floret conspicuously stipitate, or the upper floret not stipitate. The stipe beneath the upper floret when present, not filiform; straight and swollen; homogeneous. Rachilla terminated by a female-fertile floret. Hairy callus absent.

Glumes two; very unequal (the lower often minute, but up to half the spikelet length in Adenochloa); (the upper) long relative to the adjacent lemmas; hairless; awnless; non-carinate. Lower glume 0–7 nerved. Upper glume 3 nerved, or 7–13 nerved (in Adenochloa). Spikelets with incomplete florets. The incomplete florets proximal to the female-fertile florets. Spikelets with proximal incomplete florets. The proximal incomplete florets 1; male, or sterile. The proximal lemmas awnless; 3 nerved, or 5–9 nerved (Adenochloa); less firm than the female-fertile lemmas; not becoming indurated.

Female-fertile florets 1. Lemmas similar in texture to the glumes to decidedly firmer than the glumes; smooth (shiny); becoming indurated (usually?); entire; blunt; awnless; hairy (sometimes, in Adenochloa), or hairless; non-carinate; having the margins inrolled against the palea; with a clear germination flap; 3–11 nerved. Palea present; entire; awnless, without apical setae; textured like the lemma; indurated. Lodicules present; 2; free; fleshy. Stamens 3. Ovary apically glabrous. Styles free to their bases. Stigmas 2; red pigmented, or brown.

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

Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Intercostal zones with typical long-cells, or exhibiting many atypical long-cells, or without typical long-cells. Mid-intercostal long-cells having markedly sinuous walls, or having straight or only gently undulating walls. Microhairs present; panicoid-type; (45–)51–81(–93) microns long; 4.5–10.5(–12) microns wide at the septum. Microhair total length/width at septum 4.25–17.3. Microhair apical cells 21–42(–48) microns long. Microhair apical cell/total length ratio 0.37–0.57. Stomata common; 30–48 microns long. Subsidiaries low dome-shaped to triangular. Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells common, or absent or very rare; in cork/silica-cell pairs, or not paired. Costal short-cells conspicuously in long rows. Costal silica bodies ‘panicoid-type’ (sometimes sharp pointed); cross shaped to dumb-bell shaped; sharp-pointed, or not sharp-pointed.

Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll with radiate chlorenchyma; Isachne-type, or not Isachne-type. Leaf blade with distinct, prominent adaxial ribs, or ‘nodular’ in section, or adaxially flat; with the ribs more or less constant in size. Midrib not readily distinguishable; with one bundle only. Bulliforms present in discrete, regular adaxial groups (at bases of furrows); in simple fans. All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders absent (there being colourless cells linking the bundles with adaxial strands). Sclerenchyma all associated with vascular bundles.

Phytochemistry. Leaves containing flavonoid sulphates (2 species).

Special diagnostic feature. Plants from a short rosette of winter leaves, the primary panicle producing secondary inflorescences with cleistogamous spikelets.

Cytology. Chromosome base number, x = 9. 2n = 18 (mostly), or 36 (occasionally). Mostly 2 ploid.

Classification. Watson & Dallwitz (1994): Panicoideae; Panicodae; Paniceae. Soreng et al. (2015): Panicoideae; Panicodae; Paniceae; Dichelantheliinae. 120 species.

Distribution, phytogeography, ecology. Mostly America, with Adenochloa in Africa and Madagascar.

Economic aspects. Significant weed species: D. clandestinum.

References, etc. Morphological/taxonomic: Gould and Clark 1978. Leaf anatomical: studied by us - D. angustifolium (Ell.) Gould, D. clandestinum (L.) Gould, D. commutatum (Schult.) Gould, D. dichotomum (L.) Gould, D. lanuginosum (Ell.) Gould, D. lindheimeri (Nash) Gould, D. linearifolium (Scribn.) Gould, D. oligosanthes (Schult.) Gould, . scoparium (Lam.) Gould, D. sphaerocarpon (Ell.) Gould.

Illustrations. • Spikelet. Dichanthelium sp.

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: 11th December 2017.’.