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The grass genera of the world

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

Thedachloa S.W.L. Jacobs

Type species: T. annua S.W.L. Jacobs.

Habit, vegetative morphology. Annual; stoloniferous (scrambling). Culms 7–12 cm high; sparsely branched above, or unbranched above. The branching simple. Culm nodes glabrous. Leaf blades more or less triangular to 2 cm long; flat, or rolled (on drying). Ligule present; a fringe of hairs; 0.5 mm long.

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

Inflorescence. Inflorescence paniculate; contracted; dense, more or less ovoid (0.3–0.5 cm long, 0.4 cm wide); espatheate (?); not comprising ‘partial inflorescences’ and foliar organs. Spikelets solitary.

Female-fertile spikelets. Spikelets 1.7–2.1 mm long; lanceolate, or linear; compressed laterally; falling with the glumes; disarticulating between the florets. Shorter than the spikelet, the upper floret conspicuously stipitate (shortly so).

Glumes two; shorter than the spikelets, or shorter than the spikelets to about equalling the spikelets; hairy (the lower one glabrous with ciliate margins, the upper one with a band of stiff bristles above); awnless; non-carinate; very dissimilar (the lower shorter, blunt and inflated, the upper muticous with a band of stiff hairs above the middle). Lower glume convex on the back; 3 nerved. Upper glume somewhat shorter than the spikelet, 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 fully developed (cleft). The proximal incomplete florets male, or sterile. The proximal lemmas with a deep longitudinal groove, and almost tubular, with the innermost tissue of the fold absent on older florets; awnless; inflated, 7 nerved; decidedly exceeding the female-fertile lemmas (about as long as the spikelet).

Female-fertile florets 1. Lemmas elliptic, shorter than the lower one; decidedly firmer than the glumes; brown in fruit; entire; awnless; hairless; glabrous; having the margins inrolled against the palea (at least, somewhat so); with a clear germination flap to without a germination flap (weakly developed). Palea present; not indurated (membranous). Palea back glabrous.

Fruit, embryo and seedling. Fruit small (0.8 mm long). Pericarp fused. Embryo large.

Classification. Watson & Dallwitz (1994): not described separately. Soreng et al. (2015): Panicoideae; Panicodae; Paniceae. 1 species (T. annua).

Distribution, phytogeography, ecology. Northern Kimberley, Western Australia.

References, etc. Morphological/taxonomic: http://ausgrass2.myspecies.info/node/3350, Grassbase (2016), Jacobs 2003.

Special comments. Potentially of interest re photosynthetic pathway, but the requisite anatomical data (also essential to taxonomic assignment) totally lacking. Anatomical data wanting.


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

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