| # The grass genera of the world |

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

### Decaryochloa A. Camus

Habit, vegetative morphology. Monocarpic perennial. The flowering culms leafy. Culms to 10 m or more long; woody and persistent; to 2–2.5 cm in diameter; scandent to not scandent (erect with scrambling upper parts, cf. Hickelia); branched above. Primary branches 11–20; clumped. The branching dendroid. Culm leaf sheaths present; deciduous; conspicuously auriculate. Culm leaves with conspicuous blades. Culm leaf blades triangular. Pluricaespitose. Rhizomes pachymorph. Young shoots extravaginal. Leaves auriculate (these large and prominent); with auricular setae (these black and curly). Hairy. Leaf blades ovate-lanceolate; broad to narrow; 7–10 mm wide (and 5–10 cm long); pseudopetiolate; cross veined (?); rolled in bud. Ligule a fringed membrane (‘with long bristles’); truncate; about 1 mm long. Contra-ligule present.

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

Inflorescence. Inflorescence determinate; without pseudospikelets; few spikeleted; compound, with spikes of 1–4 spikelets grouped into terminal, spatheate fascicles; spatheate (each unit subtended by a bract or sheath with or without a blade, and usually with a prophyll); a complex of ‘partial inflorescences’ and intervening foliar organs. Spikelet-bearing axes spikes (straight or curved, of one to three spikelets). Spikelets solitary; not secund; sessile.

Female-fertile spikelets. Spikelets 60–70 mm long; lanceolate; compressed laterally, or compressed laterally to not noticeably compressed (?); disarticulating above the glumes; with conventional internode spacings (these very short). Rachilla shortly prolonged beyond the uppermost female-fertile floret (the extension vestigial); hairy; the rachilla extension with incomplete florets (sometimes with a conventional vestigial floret, and sometimes also enclosing a bractlike ‘extra structure’ of uncertain morphological interpretation at its base), or naked.

Glumes two to several (two to four); very unequal; shorter than the adjacent lemmas; hairy (with appressed pale hairs abaxially near the base and along one margin); pointed; awned to awnless (with pointed, rigid tips); non-carinate; very dissimilar to similar (the lowest smaller with 13 nerves, the others with 21–23 nerves). Spikelets with female-fertile florets only, or with incomplete florets. The incomplete florets when present, distal to the female-fertile florets. The distal incomplete florets merely underdeveloped.

Female-fertile florets 1. Lemmas convolute; similar in texture to the glumes (rigid, leathery, not shiny); not becoming indurated; entire; pointed (long-acuminate); awnless, or awned (?). Awns if the lemma tip so interpreted, 1; median; apical; non-geniculate; straight; much shorter than the body of the lemma. Lemmas hairy (with appressed pale hairs abaxially); non-carinate; without a germination flap; 23 nerved. Palea present; relatively long; convolute around the flower; tightly clasped by the lemma; apically notched to deeply bifid (with a long, bilobed tip); textured like the lemma (leathery, rigid); not indurated; several nerved (?); 2-keeled. Palea back hairy. Lodicules present (small). Stamens 6; with free filaments, or diadelphous (? - in two groups of three, perhaps a peculiarity in some of of Camus’s original material). Anthers about 7.5 mm long; not penicillate. Ovary apically glabrous; with a conspicuous apical appendage. The appendage broadly conical, fleshy. Styles basally fused. Stigmas 3.

Fruit, embryo and seedling. Fruit free from both lemma and palea; medium sized to large (7–14 mm long); not grooved; apically hairy. Pericarp fleshy; loosely adherent to fused. Seed endospermic. Endosperm hard.

Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll with non-radiate chlorenchyma; with arm cells; with fusoids. The fusoids external to the PBS. Leaf blade with distinct, prominent adaxial ribs, or adaxially flat (the ribs very wide and low to negligible, save for one associated with one side of the midrib). Midrib conspicuous; with one bundle only; without colourless mesophyll adaxially. The lamina distinctly asymmetrical 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; forming ‘figures’ (I’s or ‘anchors’ with most of the bundles). Sclerenchyma all associated with vascular bundles.

Classification. Watson & Dallwitz (1994): Bambusoideae; Bambusodae; Bambuseae. Soreng et al. (2015): Bambusoideae; Bambusodae; Bambuseae; Hickeliinae. 1 species (D. diadelpha).

Distribution, phytogeography, ecology. Madagascar.

Shade species. In forest.

References, etc. Morphological/taxonomic: Dransfield (1997) provides a detailed description, and shows that diadelphus stamens may be an abnormality of Camus’s material. Leaf anatomical: studied by us.

Special comments. Anatomical data for ts only.

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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