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The grass genera of the world

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

Rytidosperma Steud. sensu stricto

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

~ Danthonia sensu lato, Notodanthonia

Type species: Type: R. lechleri Steud.

Including Erythranthera Zotov, Monostachya Merr., Notodanthonia Zotov p.p., Pyrrhanthera Zotov

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

Habit, vegetative morphology. Perennial; caespitose. Culms 2–56 cm high; herbaceous; branched above, or unbranched above; 1–4 noded. Culm nodes exposed; glabrous. Culm internodes solid, or hollow. Young shoots extravaginal, or intravaginal. Leaves mostly basal, or not basally aggregated (more often); non-auriculate. Leaf blades linear, or linear-lanceolate; narrow; 0.1–4 mm wide; setaceous, or not setaceous; flat, or folded, or rolled, or acicular; hard, woody, needle-like (rarely), or not needle-like; exhibiting multicellular glands abaxially. The abaxial leaf blade glands intercostal. Leaf blades without cross venation; disarticulating from the sheaths, or persistent; once-folded in bud. Ligule a fringed membrane (very short), or a fringe of hairs; 0.5–5 mm long. Contra-ligule present, or absent.

Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets. The spikelets all alike in sexuality. Plants inbreeding; exposed-cleistogamous, or chasmogamous; without hidden cleistogenes.

Inflorescence. Inflorescence rarely reduced to a single spikelet, or few spikeleted (usually), or many spikeleted; paniculate (sometimes almost a raceme, or reduced to a single spikelet); open to contracted (frequently open at anthesis, then closing when fruiting); espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes persistent. Spikelets not secund; pedicellate.

Female-fertile spikelets. Spikelets 3–17 mm long; cuneate, or obovate; green to purple; compressed laterally; disarticulating above the glumes; disarticulating between the florets (the disarticulations oblique); with conventional internode spacings. Rachilla prolonged beyond the uppermost female-fertile floret; hairless; the rachilla extension with incomplete florets. Hairy callus present. The callus hairs white. Callus short; blunt.

Glumes two; more or less equal; about equalling the spikelets, or exceeding the spikelets; long relative to the adjacent lemmas; usually hairy, or hairless (rarely); scabrous; pointed (acute); awnless; keeled above; similar (papery, persistent). Lower glume 5–7 nerved. Upper glume 5–7 nerved. Spikelets with female-fertile florets only, or with incomplete florets. The incomplete florets when present, as is usual, distal to the female-fertile florets. The distal incomplete florets merely underdeveloped. Spikelets without proximal incomplete florets.

Female-fertile florets 2–8. Lemmas similar in texture to the glumes (soft to leathery); not becoming indurated; entire, or incised; pointed; 2 lobed (the lobes acute, acuminate or setaceous, often partially fused to the awn base); deeply cleft, or not deeply cleft; rarely mucronate, or awned. Awns 1, or 3; median, or median and lateral; the median different in form from the laterals (when laterals present); from a sinus; non-geniculate, or geniculate; much shorter than the body of the lemma to much longer than the body of the lemma; entered by several veins. The lateral awns (when present) shorter than the median to about equalling the median (straight, terminating the lobes). Lemmas nearly always hairy (though there are a few exceptions). The hairs when present (as is usual), in tufts; in transverse rows (usually with transverse rows of tufts, or as two marginals tufts). Lemmas non-carinate (rounded on the back); without a germination flap; 7–9 nerved; with the nerves confluent towards the tip. Palea present; relatively long; entire (truncate), or apically notched (minutely bilobed); awnless, without apical setae; thinner than the lemma; not indurated (membranous, or firm towards the base); 2-nerved; 2-keeled. Palea back glabrous, or hairy. Palea keels wingless; scabrous. Lodicules present; 2; free; fleshy; ciliate; not or scarcely vascularized. Stamens 3. Anthers 0.3–3 mm long; not penicillate. Ovary apically glabrous. Styles free to their bases; free. Style bases widely separated. Stigmas 2; white, or red pigmented, or brown.

Fruit, embryo and seedling. Disseminule a caryopsis enclosed in but free of the lemma and palea. Fruit free from both lemma and palea; small; golden-brown; obovate; longitudinally grooved (or somewhat hollowed); compressed dorsiventrally; glabrous; smooth. Hilum short (usually punctiform). Pericarp thin; fused. Embryo large; waisted; without an epiblast; with a scutellar tail; with an elongated mesocotyl internode.

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

Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Long-cells similar in shape costally and intercostally; of similar wall thickness costally and intercostally. Intercostal zones with typical long-cells. Mid-intercostal long-cells rectangular; having markedly sinuous walls. Microhairs present, or absent; panicoid-type, or chloridoid-type; 45–54–66 microns long; 9.6–18.22–26.4 microns wide at the septum. Microhair total length/width at septum 1.8–3.325–5.8. Microhair apical cells 13.5–24.75–36 microns long. Microhair apical cell/total length ratio 0.3–0.4425–0.59. Stomata common, or absent or very rare; 39–43.5–48 microns long. Subsidiaries dome-shaped, or triangular; not including both parallel-sided and triangular forms on the same leaf. Guard-cells overlapped by the interstomatals, or overlapping to flush with the interstomatals. Intercostal short-cells common; in cork/silica-cell pairs; silicified, or not silicified. Intercostal silica bodies crescentic. Crown cells absent. Costal zones with short-cells. Costal short-cells conspicuously in long rows, or predominantly paired, or neither distinctly grouped into long rows nor predominantly paired. Costal silica bodies rounded, or crescentic, or ‘panicoid-type’; cross shaped; not sharp-pointed.

Transverse section of leaf blade, physiology. Leaf blades ‘laminar’.

C3; XyMS+. Mesophyll with radiate chlorenchyma, or with non-radiate chlorenchyma; without adaxial palisade; not Isachne-type; without ‘circular cells’; not traversed by colourless columns; without arm cells; without fusoids. Leaf blade with distinct, prominent adaxial ribs, or adaxially flat; with the ribs more or less constant in size. Midrib conspicuous, or not readily distinguishable; with one bundle only; without colourless mesophyll adaxially. Bulliforms present in discrete, regular adaxial groups, or not present in discrete, regular adaxial groups; in simple fans; nowhere involved in bulliform-plus-colourless mesophyll arches. Many of the smallest vascular bundles unaccompanied by sclerenchyma, or all the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present; forming ‘figures’. Sclerenchyma all associated with vascular bundles.

Cytology. Chromosome base number, x = 6. 2n = 24, 48, 72, 96, and 120. 4–20 ploid.

Classification. Watson & Dallwitz (1994): Arundinoideae; Danthonieae. Soreng et al. (2015): Danthonioideae; Danthonieae. 35 species.

Distribution, phytogeography, ecology. Australasian region, and perhaps also South America.

Tasmania, New South Wales, Australian Capital Territory, Victoria, New Guinea, and New Zealand.

Helophytic, or mesophytic; mostly species of open habitats; glycophytic. Generally open, upland, grasslands, mires or rocky habitats.

References, etc. Morphological/taxonomic: Rytidosperma as re-circumscribed by H.P. Linder, who provided the description (1997: excluding anatomy). Leaf anatomical: This project. Data temporarily restricted to the included genera, Erythranthera, Monostachya, and Pyrrhanthera, pending reorganization of the anatomical description of Rytidosperma sensu Linder.

Illustrations. • R. caespitosum, as Danthonia: Kunth (1835). • Rytidosperma gracile (as Danthonia): Hooker, Fl. Novae-Zelandiae (1853). • Rytidosperma setaceum (as Danthonia): Hooker, Fl. Tasmaniae (1860). • R. pauciflorum (as Danthonia): Hooker, Fl. Tasmaniae (1860). • 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. • Abaxial epidermis of leaf blade of R. (Monostachya) oreoboloides: this project. • Abaxial epidermis of leaf blade of R. (Pyrrhanthera) exigua: this project. • Abaxial epidermis of leaf blade (Pyrrhanthera exigua). • ‘Panicoid-type’ microhairs of R. linkii and Peudosasa japonica: longitudinal EM sections (Amarasinghe)


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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: 13th November 2017. delta-intkey.com/grass’.

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