|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.
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)
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.)
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.
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.
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.