| # The grass genera of the world |

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

### Dallwatsonia B.K. Simon

Named for M.J.Dallwitz and L.Watson.

~ Hymenachne

Type species: Type: D. felliana B.K.Simon.

Habit, vegetative morphology. Perennial. Culms 40–130 cm high; herbaceous; branched above; 7 noded. Leaf blades linear, or linear-lanceolate. Ligule a fringed membrane.

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

Inflorescence. Inflorescence of spicate main branches, or paniculate (the main axis to 22 cm long, the primary branches to 6 cm, the spikelet bearing branches reduced to 2-several spikelets); non-digitate. Primary inflorescence branches inserted all around the main axis. Inflorescence espatheate; not comprising ‘partial inflorescences’ and foliar organs. The racemes spikelet bearing to the base. Spikelet-bearing axes persistent. Spikelets unaccompanied by bractiform involucres, not associated with setiform vestigial branches; more or less paired; secund to not secund (the spikelet bearing branches on two sides of the three-sided rachis); pedicellate (the pedicels 0.1–4 mm long). Pedicel apices cupuliform. Spikelets not imbricate; somewhat consistently in ‘long-and-short’ combinations; unequally pedicellate in each combination.

Female-fertile spikelets. Spikelets 3.5–4 mm long; elliptic, or lanceolate; adaxial; somewhat compressed laterally; falling with the glumes; not disarticulating between the florets; with conventional internode spacings. The upper floret not stipitate. Rachilla terminated by a female-fertile floret. Hairy callus absent. Callus absent.

Glumes two; very unequal (the lower much shorter); (the upper) consistently somewhat shorter than the spikelets; shorter than the adjacent lemmas; hairless; glabrous; pointed; awnless; non-carinate (but with raised nerves); very dissimilar (membranous, the lower ovate and much shorter, the upper lanceolate and almost as long as the L1). Lower glume 0.3–0.5 times the length of the upper glume; shorter than the lowest lemma; much shorter than half length of lowest lemma; convex on the back; relatively smooth; 5 nerved. Upper glume not saccate; 5–7 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 (no more than half the lemma length, linear or lanceolate, hyaline); not becoming conspicuously hardened and enlarged laterally. The proximal incomplete florets sterile. The proximal lemmas lanceloate, membranous, resembling the upper glume; awnless; 5 nerved; more or less equalling the female-fertile lemmas to decidedly exceeding the female-fertile lemmas; less firm than the female-fertile lemmas to similar in texture to the female-fertile lemmas; not becoming indurated.

Female-fertile florets 1. Lemmas lanceolate; not saccate; similar in texture to the glumes to decidedly firmer than the glumes (membranous to very thinly cartilaginous); smooth; not becoming indurated; white in fruit; entire; pointed; not deeply cleft; not crested; awnless; hairless; glabrous; non-carinate (rounded on the back); having the margins lying flat on the palea; with a clear germination flap; 5–7 nerved (the median lacking or basal only in the material seen); with the nerves non-confluent. Palea present; relatively long; gaping; entire; awnless, without apical setae; textured like the lemma; not indurated; 2-nerved; keel-less. Palea back glabrous. Lodicules present; 2; free; fleshy; glabrous; not or scarcely vascularized. Stamens 3. Anthers 1.4–2 mm long; not penicillate; without an apically prolonged connective. Ovary apically glabrous; without a conspicuous apical appendage. Styles free to their bases; free. Style bases widely separated. Stigmas 2.

Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Long-cells markedly different in shape costally and intercostally (the costals much narrower); of similar wall thickness costally and intercostally (the walls of medium thickness). Mid-intercostal long-cells rectangular; having markedly sinuous walls. Microhairs present; elongated; clearly two-celled; panicoid-type (broad, almost balanoform); 50–55 microns long; about 10 microns wide at the septum. Microhair total length/width at septum 5–5.5. Microhair apical cells 35–40 microns long. Microhair apical cell/total length ratio 0.7–1. Stomata common; 15–20 microns long. Subsidiaries non-papillate; dome-shaped and triangular. Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells common; in cork/silica-cell pairs (mostly), or not paired (some solitary); silicified and not silicified. Intercostal silica bodies mostly more or less cross-shaped. With a few small intercostal prickles. Costal short-cells conspicuously in long rows. Costal silica bodies present and well developed; ‘panicoid-type’; short to medium dumb-bell shaped, or nodular (a few only).

Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll seemingly Isachne-type (at least in places); not traversed by colourless columns; without fusoids (but most of the intercostal zones with a well defined aerenchymatous region in the middle). Leaf blade ‘nodular’ in section to adaxially flat. Midrib conspicuous (the keel large and abaxially prominent); having a conventional arc of bundles (the large median accompanied on either side by several small laterals); with colourless mesophyll adaxially. The lamina symmetrical on either side of the midrib. Bulliforms present in discrete, regular adaxial groups; in simple fans. All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present (with all or most of the lateral bundles); forming ‘figures’ (some of the configurations somewhat I-shaped). Sclerenchyma all associated with vascular bundles.

Classification. Watson & Dallwitz (1994): Panicoideae; Panicodae; Paniceae. Soreng et al. (2015): Panicoideae; Panicodae; Paspaleae; Otachyriinae. 1 species (D. felliana).

Distribution, phytogeography, ecology. Queensland.

Helophytic; glycophytic.

References, etc. Morphological/taxonomic: B.K. Simon 1992. Leaf anatomical: D. felliana only, studied by us.

Special comments. This description does not account for the relatively recent transfer from Panicum of some 10 species from South and Central America, West Indies, India, China, New Guinea ... Fruit data wanting.

Illustrations. • General aspect, inflorescence, spikelet and florets of Dallwatsonia felliana. • Spikelet of D. felliana. • Dallwatsonia felliana, abaxial epidermis of leaf blade: this project. • Dallwatsonia felliana, abaxial epidermis of leaf blade: this project. • Dallwatsonia felliana, abaxial epidermis of leaf blade: this project.

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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