Vascular Plants of Williamson County

Dactyloctenium aegyptium [Poaceae]
crowfoot grass, durban crowfoot

Dactyloctenium aegyptium (L.) Willd., crowfoot grass, durban crowfoot. Annual, fibrous–rooted, several–stemmed at base, matlike, ± decumbent forming adventitious roots at lower nodes, 20—40+ cm tall; shoots often bent upward at 1 or 2 nodes along stem, somewhat scabrous.

Stems (culms)

Stems (culms) elliptic in ×–section, to 3 mm diameter, tough, glabrous; nodes and internodes solid.

Leaves

Leaves alternate distichous, simple with sheath; sheath open, typically < internode, without lobes (auricles) at top; ligule densely hairy but membranous at base, ca. 0.3 mm long; blade linear–lanceolate, 25—70(—150) × 2.5—6 mm, the widest near base, ± flat, collar white with short hairs on lower surface, entire and ciliate with long, bulbous–based hairs to midpoint on margins and minutely toothed approaching tip, parallel–veined with midrib but not raised on lower surface, scabrous along principal veins approaching tip.

Inflorescence

Inflorescence spikelets, in terminal umbel–like panicles of 2—4(—5) spreading to ascending branches (spikes), spikes 10—35(—50) mm long, bristle–tipped, 1–sided with spikelets in 2 overlapping rows on upper side, spikelet of (1—)2—3–florets (terminal floret often sterile), spikelets absent on terminal 2—4 mm of axis; tip of peduncle and bases of spikes silky–hairy; spike rachis triangular in ×–section, green with whitish or tannish edges, silky–hairy between spikelets.

Spikelet

Spikelet compressed side–to–side and ⊥ rachis axis, short–awned; glumes 2, awned, subequal, 1.5—2 mm long, keeled, membranous aging dark gray in fruit, 1–veined, lower glume acute or short–pointed at tip, upper glume awned at tip, the awn wavy to curved or straight and 1—2 mm long, minutely toothed primarily along inner edges; lemma ovate with sharp point at tip, ± 3.5 mm long, keeled, membranous with conspicuous green vein along keel and 1 faint vein near each margin, with minute teeth along keel; palea < lemma, 2–keeled, membranous, concave between keels, short–ciliate along keels.

Flower

Flower bisexual; perianth (lodicules) 2, ± deltate (narrow at base) with a lateral projection and wavy tip, ca 0.3 mm long, whitish; stamens 3, free; filaments threadlike, ca. 3 mm long, white; anthers exserted, basifixed, dithecal, 0.2—0.4 mm long, white, longitudinally dehiscent; pollen white; pistil 1; ovary superior, ovoid, white, minutely warty, glabrous, 1–chambered with 1 ovule; styles 2, ± feathery (plumose), exserted slightly from lemma tip and touching anthers

Fruit

Fruit achene (caryopsis) sandgrainlike, 1.5 mm long, gray, cobblestonelike, hard.

A. C. Gibson & B. A. Prigge