17.29   DACTYLOCTENIUM Willd.
Stephan L. Hatch

Plants annual or perennial; tufted, stoloniferous, or rhizomatous. Culms 5-115(160) cm, erect or decumbent, often rooting at the lower nodes, not branching above the base. Sheaths not overlapping, open, keeled; auricles absent; ligulesmembranous, membranous and ciliate, or of hairs; blades flat or involute. Inflorescences terminal, panicles of 2-11, digitately arranged spicate branches; branches with axes 0.8-11 cm long, extending beyond the spikelets, terminating in a point, the spikelets imbricate in 2 rows on the lower sides. Spikelets with 3-7 bisexual florets, additional sterile florets distally; disarticulationusually above the glumes, the florets falling as a unit. Glumes unequal, shorter than the adjacent lemmas, 1-veined, keeled; lower glumes acute, mucronate; upper glumes subapically awned, awns curved; calluses glabrous; lemmas membranous, glabrous, 3-veined (lateral veins sometimes indistinct), strongly keeled, apices entire, mucronate, or awned; paleas glabrous; anthers 3, yellow; ovaries glabrous; styles fused. Fruit utricles; seeds falling free of the hyaline pericarp, transversely rugose or granular. x = 10. Name from the Greek daktylos, finger, and ktenion, a little comb, describing the comblike inflorescence branches.

Dactyloctenium is primarily an African and Australian genus of 10-13 species. Three species have been introduced in the Flora region, two of which have become established. Dactyloctenium aegyptium is widespread throughout the warmer areas of the world.


SELECTED REFERENCES Black, J.M.1978. Gramineae. Pp. 88-249 in J.M. Black. Flora of South Australia, Part I, ed. 3 (rev. J.P. Jessop). D.J. Woolman, Government Printer, Adelaide, South Australia, Australia. 466 pp.; Clayton, W.D., S.M. Phillips, and S.A. Renvoize. 1974. Flora of Tropical East Africa. Gramineae (Part 2) (ed. R.M. Pohill). Whitefriars Press, Ltd., London, England. 373 pp.; Jacobs, S.W.L. and S.M. Hastings. 1993. Dactyloctenium. Pp. 527-529 in G.J. Harden (ed.). Flora of New South Wales, vol. 4. New South Wales University Press, Kensington, New South Wales, Australia. 775 pp.; Koekemoer, M. 1991. Dactyloctenium Willd. Pp. 99-101 in G.E. Gibbs Russell, L. Watson, M. Koekemoer, L. Smook, N.P. Barker, H.M. Anderson, and M.J. Dallwitz. Grasses of Southern Africa (ed. O.A. Leistner). National Botanic Gardens, Botanical Research Institute, Pretoria, Republic of South Africa. 437 pp.

1
Panicle branches 0.4-1.5 cm long; most spikelets touching those of an adjacent branch ..... 2. D. radulans
Panicle branches 1.5-7 cm long; only the first few proximal spikelets on each branch in contact with those on an adjacent branch (2)
2
Anthers 0.5-0.9 mm long; upper glume awns 1-2.5 mm long ..... 1. D. aegyptium
Anthers 1.1-1.7 mm long; upper glume awns 4.5-10 mm long ..... 3. D. geminatum


1.   Dactyloctenium aegyptium (L.) Willd.
Durban Crowfoot

Plants tufted annuals or short-lived, shortly stoloniferous perennials. Culms 10-35(100) cm, usually geniculately ascending and rooting at the lower nodes. Sheaths keeled, with papillose-based hairs distally; ligules 0.5-1.5 mm, membranous, ciliate; blades 5-22 cm long, 2-8(12) mm wide, with papillose-based hairs. Panicle branches (1)2-6(8), 1.5-6 cm, only the first few spikelets in contact with the spikelets of adjacent branches; branch axes extending beyond the spikelets for 1-6 mm. Spikelets 3-4.5 mm long, about 3 mm wide. Glumes 1.5-2 mm; lower glumes ovate, acute; upper glumes oblong elliptic, obtuse, awned, awns 1-2.5 mm; lemmas 2.5-3.5 mm, ovate, midveins extended into curved, 0.5-1 mm awns; paleas about as long as the lemmas; anthers 0.5-0.8 mm, pale yellow. Seeds cuboid, about 1 mm long and wide, transversely rugose, light tan to reddish-brown. 2n = 20, 36, 40, 45, 48.

Dactyloctenium aegyptium is a widely distributed weed of disturbed sites in the Flora region. It is also considered a weed in southern Africa, but the seeds have been used for food and drink in times of famine. In addition, bruised young seeds have been used as a fish poison, and extracts are reputed to help kidney ailments and coughing (Koekemoer 1991). In Australia, it is planted as a sand stabilizer along the coast (Jacobs and Hastings 1993).


2.   Dactyloctenium radulans (R. Br.) P. Beauv.
Buttongrass

Plants annuals or short-lived perennials. Culms 5-20(50) cm, decumbent or ascending, rarely erect, usually branched. Sheaths glabrous or with papillose-based hairs, slightly keeled; ligules to 1 mm, membranous, truncate, ciliate; blades flat, bases with papillose-based hairs. Panicle branches 2-11, 0.4-1.5 cm, almost globose, most of the spikelets in contact with the spikelets of adjacent branches; branch axes extending beyond the distal spikelets as 1-1.5 mm points. Spikelets 3.5-5 mm, with 2-5 florets. Glumes strongly keeled; lower glumes 1-2 mm, ovate, acute; upper glumes 1.5-3 mm, oblong elliptic, acuminate, awned, awns 0.5-2.5 mm; lemmas 3-4.3 mm, ovate, keels scabrous, 1-veined, veins excurrent about 0.5 mm, apices acuminate to mucronate; paleas shorter than the lemmas; anthers 0.2-0.8 mm, pale yellow. Seedsabout 1.2 mm long, about 0.7 mm wide, transversely rugose, brown. 2n = unknown.

Dactyloctenium radulans has been found at few locations in the Flora region, most of which were associated with wool waste. It is native to Australia, where it is regarded as a valuable ephemeral pasture grass in the drier inland areas but also as a garden weed. It resembles Dactyloctenium aristatum Link of tropical eastern Africa, differing primarily in having transversely rugose, rather than granular, caryopses.


3.   Dactyloctenium geminatum Hack.
Double Combgrass

Plants perennial; stoloniferous, mat-forming. Culms 35-112 cm, ascending. Blades 4-25 cm long, 3-6 mm wide, flat, more or less glabrous. Panicle branches (1)2(3), 2.5-7 cm, often slightly falcate, only the first few spikelets in contact with the spikelets of adjacent branches. Spikelets 3-5.3 mm, with 3-6 florets. Glumes subequal, 1.3-1.8 mm, widely elliptic to ovate or obovate in profile, awned, awns 4.5-10 mm; lemmas 3-3.8 mm, lanceolate, keels smooth or finely scabridulous towards the acute or mucronate apices; palea keels not winged; anthers 1.1-1.7 mm. Seeds about 1 mm long, transversely rugose. 2n = unknown.

Dactyloctenium geminatum is native to tropical eastern Africa. It was found at one time on ballast dumps in Maryland, but has not survived in North America.