| # The grass genera of the world |

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

### Rytidosperma Steud. sensu Linder et al. (2010)

From the Greek rhytis (wrinkle) and sperma (seed), referring to the back of a larvae mistaken for the seed.

~ Danthonia sensu lato

Type species: R. lechleri Steud.

Including Austrodanthonia H.P. Lind., Danthonia sect. Eudanthonia Benth., Erythranthera Zotov, Joycea H.P. Linder, Monostachya Merr., Notodanthonia Zotov, Pyrrhanthera Zotov, Thonandia H.P. Linder

Excluding Austrodanthonia, Chionochloa, Joycea, Karroochloa, Merxmuellera, Monachather, Notodanthonia p.p., Plinthanthesis

Habit, vegetative morphology. Perennial; not reedy; rhizomatous (3/6), or caespitose (6/6), or decumbent (2/6). The flowering culms leafless (2/2). Culms 1–37.78–160 cm high; herbaceous (6/6); cylindrical (3/3); branched above (1/4), or unbranched above (4/4); 1 noded (2/4), or 2–4 noded (4/4), or 5 noded (2/4), or 6–7 noded (1/4). Culm nodes exposed (4/4); glabrous. Culm leaves absent (1/1). Culm internodes solid (5), or hollow (3). Plants without multicellular glands. Young shoots extravaginal (3/4), or intravaginal (4/4). The shoots not aromatic. Leaves mostly basal, or not basally aggregated (1); non-auriculate; without auricular setae. Sheath margins free. Leaf blades linear (1/4), or linear-lanceolate (4/4); narrow; 0.1–4.325–20 mm wide; not cordate, not sagittate; setaceous (4), or not setaceous (5); flat (5/6), or folded (3/6), or rolled (1/6), or acicular (1/6); hard, woody, needle-like (very rarely), or not needle-like; without abaxial multicellular glands (1/2), or exhibiting multicellular glands abaxially (1/2). The abaxial leaf blade glands intercostal (1/1). Leaf blades without cross venation; disarticulating from the sheaths (2), or persistent (6); once-folded in bud (1/1). Ligule a fringed membrane (2/6), or a fringe of hairs (usually, 6/6); not truncate (1/1); 0.5–2.75–5 mm long. Contra-ligule present (1/4), or absent (4/4).

Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets. The spikelets of sexually distinct forms on the same plant (1), or all alike in sexuality; hermaphrodite, or sterile (1). Plants inbreeding (1/1); exposed-cleistogamous (1), or chasmogamous; without hidden cleistogenes. Not viviparous (2/2).

Inflorescence. Inflorescence reduced to a single spikelet (3), or few spikeleted (4), or many spikeleted (4); of spicate main branches (1), or a single raceme (3), or paniculate (6; i.e., the panicle sometimes almost a raceme, or reduced to a single spikelet); open (5/5), or contracted (3/5), or open to contracted (often closing when fruiting); more or less irregular (3/3); without capillary branchlets (6/6); non-digitate; espatheate; not comprising ‘partial inflorescences’ and foliar organs (6/6). Spikelet-bearing axes solitary (1/1); persistent. Spikelets solitary (3/3); not secund (6/6); pedicellate (6/6); not imbricate (2/2).

Female-sterile spikelets. The staminal filaments free (1/1).

Female-fertile spikelets. Spikelets 2.5–11.18–25 mm long; cuneate (4/4), or elliptic (1/4), or obovate (1/4); green to purple; compressed laterally; disarticulating above the glumes; disarticulating between the florets (5/5); with conventional internode spacings (usually, 5/6), or with distinctly elongated rachilla internodes between the florets (1/6). The upper floret not stipitate (1/1). Rachilla prolonged beyond the uppermost female-fertile floret; hairy (1/6), or hairless (6/6); the rachilla extension with incomplete florets (4/4). Hairy callus present (5), or absent (3). The callus hairs white (3/3). Callus short (5/6), or long (2/6); blunt (5/5).

Glumes two; more or less equal; shorter than the spikelets (1/5), or about equalling the spikelets (3/5), or exceeding the spikelets (4/5); long relative to the adjacent lemmas; hairy (1/5), or hairless (5/5); glabrous (1/5), or scabrous (4/5); without conspicuous tufts or rows of hairs; pointed (4/4); not subulate (3/3); awnless; carinate (above, 3/3); similar (papery, persistent). Lower glume much exceeding the lowest lemma (3/3); relatively smooth (1/1); 1–2 nerved (1), or 3 nerved (5), or 4 nerved (4), or 5 nerved (5), or 6 nerved (4), or 7 nerved (5), or 8–9 nerved (2), or 10–13 nerved (1). Upper glume 1–2 nerved (1), or 3 nerved (5), or 4 nerved (3), or 5–6 nerved (4), or 7 nerved (5), or 8–9 nerved (2), or 10–13 nerved (1). Spikelets with female-fertile florets only (4), or with incomplete florets (rarely). The incomplete florets when present, as is usual, distal to the female-fertile florets. The distal incomplete florets merely underdeveloped (5/5); awnless (3/3). Spikelets without proximal incomplete florets.

Female-fertile florets (1–)2–8(–10). Lemmas similar in texture to the glumes (soft to leathery, 4/4); smooth (3/3), or striate (1/3); not becoming indurated; white in fruit (3/3); entire (1), or incised; pointed (1/1); 2 lobed (5), or 3 lobed (2; the lobes acute, acuminate or setaceous, often partially fused to the awn base); deeply cleft (4/6), or not deeply cleft (3/6); awnless (1), or mucronate (3), or awned (5). Awns 1 (4/4), or 3 (4/4); median (4/4), or median and lateral (4/4); with the median different in form from the laterals (3/3, when laterals present); from a sinus (5/5); non-geniculate (3/5), or geniculate (4/5); straight (1/1); hairless (3/3); much shorter than the body of the lemma (3/5), or about as long as the body of the lemma (2/5), or much longer than the body of the lemma (4/5); entered by several veins (4/4). The lateral awns when present, terminating the lobes, shorter than the median (1/1), or about equalling the median (1/1). Awn bases twisted (3/3); flattened (3/3). Lemmas hairy (6), or hairless (2). The hairs in tufts (2/6), or not in tufts (4/6); in transverse rows (2/6: usually with transverse rows of tufts, or as two marginal tufts), or not in transverse rows (4/6). Lemmas carinate (1), or non-carinate. The keel wingless (1/1). Lemmas without a germination flap (4/4); 3–5 nerved (1), or 7–8 nerved (2), or 9 nerved (6); with the nerves confluent towards the tip (4/4). Palea present; relatively long (4/4); tightly clasped by the lemma (2/2); entire (truncate, 3/4), or apically notched (minutely bilobed, 4/4); awnless, without apical setae (4/4); thinner than the lemma (4/4); not indurated (membranous or firm towards the base, 4/4); 2-nerved; 2-keeled (5/5). Palea back glabrous (4/4), or scabrous (1/4), or hairy (4/4). Palea keels wingless (3/3); scabrous (4/5), or hairy (3/5). Lodicules present; 2 (6/6); joined (1), or free; fleshy, or membranous (1); ciliate (6), or glabrous (2); toothed (1/1); not or scarcely vascularized (4/4). Stamens 3. Anthers 0.2–1.912–5.2 mm long; not penicillate (4/4). Ovary apically glabrous; without a conspicuous apical appendage. Styles free to their bases; free (4/4). Style bases widely separated (4/4). Stigmas 2; white (3/5), or red pigmented (2/5), or brown (2/5).

Fruit, embryo and seedling. Disseminule a caryopsis enclosed in but free of the lemma and palea (4/4). Fruit free from both lemma and palea (4/4); small; fusiform (1/1); longitudinally grooved (1), or not grooved (or only somewhat hollowed, 6); compressed laterally (1/6), or compressed dorsiventrally (5/6); glabrous (4/4). Hilum short. Pericarp thin (nearly always, 6), or thick and hard (1); free (1), or fused (usually, 6). Embryo large (6), or small (1); waisted (5/6), or not waisted (1/6). Endosperm containing compound starch grains (1/1). Embryo without an epiblast (3/3); with a scutellar tail (3/3); with an elongated mesocotyl internode (2/2).

Ovule, embryology. Micropyle not noticeably oblique (3/3). Outer integument covering no more than the chalazal half of the ovule (3/3); more than two cells thick at the micropylar margin (3/3). Inner integument discontinuous distally (4/4); not thickened around the micropyle (3/3). Synergids haustorial (strongly develoed, 4/4); exhibiting large, globular starch grains (3/3).

Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous (4/4). Papillae absent (4/4). Long-cells similar in shape costally and intercostally (4/4); of similar wall thickness costally and intercostally (4/4). Intercostal zones with typical long-cells. Mid-intercostal long-cells rectangular (3/3); having markedly sinuous walls (4/4). Microhairs present (3/4), or absent (2/4); panicoid-type (3/3), or chloridoid-type (2/3); 45–54.5–66 microns long; 9.6–18.15–26.4 microns wide at the septum. Microhair total length/width at septum 1.8–3.483–5.8. Microhair apical cells 13.5–24.75–36 microns long. Microhair apical cell/total length ratio 0.3–0.4433–0.59. Stomata common (2/4), or absent or very rare (3/4); 39–43.5–48 microns long. Subsidiaries dome-shaped (3/3), or triangular (3/3); not including both parallel-sided and triangular forms on the same leaf. Guard-cells overlapped by the interstomatals (2/2), or overlapping to flush with the interstomatals (2/2). Intercostal short-cells common (4/4); in cork/silica-cell pairs (4/4); silicified (3/4), or not silicified (2/4). Intercostal silica bodies crescentic (2/2). Costal short-cells conspicuously in long rows (3/4), or predominantly paired (2/4), or neither distinctly grouped into long rows nor predominantly paired (3/4). Costal silica bodies rounded (4/4), or crescentic (3/4), or ‘panicoid-type’ (3/4); cross shaped (2/2).

Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll with radiate chlorenchyma (2/4), or with non-radiate chlorenchyma (4/4); without adaxial palisade (3/3). Leaf blade with distinct, prominent adaxial ribs (3/4), or adaxially flat (3/4); with the ribs more or less constant in size (3/3). Midrib conspicuous (3/4), or not readily distinguishable (3/4); with one bundle only (4/4). Bulliforms present in discrete, regular adaxial groups (2/3), or not present in discrete, regular adaxial groups (2/3); in simple fans (2/2). Many of the smallest vascular bundles unaccompanied by sclerenchyma (2/4), or all the vascular bundles accompanied by sclerenchyma (3/4). Combined sclerenchyma girders present (4/4); forming ‘figures’ (4/4). Sclerenchyma all associated with vascular bundles (5/5).

Cytology. Chromosome base number, x = 5 (1/5), or 6 (3/5), or 12 (1/5). 2n = 12–30–120. 2 ploid (2/5), or 4 ploid (4/5), or 5 ploid (1/5), or 6 ploid (2/5), or 7 ploid (1/5), or 8 ploid (2/5), or 9–20 ploid (1/5).

Classification. Watson & Dallwitz (1994): Arundinoideae; Danthonieae. Soreng et al. (2015): Danthonioideae (3/3); Danthonieae (3/3). About 75 species.

Distribution, phytogeography, ecology. In cool and cool-temperate habitats in New Guinea, Australia, New Zealand, South America.

Helophytic (1/4), or mesophytic (4/4); shade species (1/6), or species of open habitats (5/6); glycophytic (5/5). Generally open, upland, grasslands, mires or rocky habitats.

Rusts and smuts. Rusts — no rusts recorded.

References, etc. Morphological/taxonomic: cf. Watson & Dallwitz (1994), edited by cross referencing with subsequent Linder et al. papers. Leaf anatomical: data representing observations on the segregate genera studied by us (Erythranthera, Joycea, Monostachya, Notodanthonia, Pyrrhanthera), supplemented from Metacalfe's less than usually detailed descriptions (1960) of species here referred to Rytidosperma).

Special comments. Where more than one character state of an applicable character is exhibited by this version of Rytidosperma sensu lato, the distribution of states with reference to the Rytidosperma sensu stricto version (q.v.) and the segregate genera (q.v.) is indicated by ‘comments’.

Illustrations. • R. caespitosum, as Danthonia: Kunth (1835). • R. gracile (as Danthonia): Hooker, Fl. Novae-Zelandiae (1853). • R. setaceum (as Danthonia): Hooker, Fl. Tasmaniae (1860). • R. pauciflorum (as Danthonia): Hooker, Fl. Tasmaniae (1860). • Rytidosperma caespitosum: Linder et al, Ann. Miss. Bot. Gard. 97 (2010). • R. carphoides, as Danthonia: Turner, Austr. Grasses (1895). • R. carphoides, abaxial epidermis of leaf blade: this project. • R. carphoides, abaxial epidermis of leaf blade: this project. • R. dimidiata, abaxial epidermis of leaf blade: this project. • R. nivicola, abaxial epidermis of leaf blade: this project. • R. nivicola, abaxial epidermis of leaf blade: this project. • R. procera, abaxial epidermis of leaf blade: this project. • procera, abaxial epidermis of leaf blade: this project. • R. nudiflora, abaxial epidermis of a leaf blade with external pitting: external. • R. (Monostachya) oreoboloides, abaxial epidermis of leaf blade: this project. • R. (Pyrrhanthera) exigua, abaxial epidermis of leaf blade: this project. Pyrrhanthera (Rytidosperma) exigua. • ‘Panicoid-type’ microhairs of R. linkii and Peudosasa japonica: longitudinal EM sections (Amarasinghe). Longitudinal sections showing ultrastructure of ‘panicoid-type’ microhairs of Pseudosasa japonica (Figs. 26–28) and Rytidosperma linkii (29–30). BC = basal cell, CC = cap cell, CW = cell wall, D = dictyosomes, M = mitochondria, N = nucleus, OS = osmophilic material, PM = plasma membrane, RER = rough endoplasmic reticulum. Scale bars: Fig. 26, 1.5 microns; 27, 1 micron; 28, 0.1 micron; 29, 2 microns; 30, 1 micron.

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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