10.14 AMELICHLOA Arriaga & Barkworth
Mirta O. Arriaga

Plants perennial; cespitose. Culms erect, with 2–3 nodes, not branching at the upper nodes; basal branching intravaginal; prophylls concealed by the leaf sheaths, winged over the keels, apices bifid, teeth 0.5–3.5 mm. Leaves mostly basal; sheaths open, smooth, glabrous; cleistogenes often present, spikelets of cleistogenes 0.5–1 mm long, with thin glumes shorter than the florets, florets unawned or with reduced awns; auricles absent; ligules scarious, rounded to acute, ciliate; blades stiff, involute, apices stiff, brown, sharply pointed, blades of the flag leaves 5–13 cm long, bases similar in width to the top of the sheaths. Inflorescences panicles, the main panicle terminal, apparently wholly chasmogamous. Spikelets with 1 floret; disarticulation above the glumes, beneath the floret. Glumes exceeding the floret, acute to acuminate, 1–5-veined; florets fusiform, terete; calluses antrorsely strigose, blunt; lemmas pubescent, often more densely and/or more persistently so over the midvein and lateral veins, hairs on the proximal portion about 0.7–2 mm, hairs on the distal portion often longer; crowns not developed; awns once- or twice-geniculate, scabrous, persistent; paleas 3/4 as long as to almost equaling the lemmas, flat, hairy, hairs 0.2–1 mm, veins terminating at or near the apices, apices similar in texture to the body; lodicules 3; anthers 3, anthers sometimes all of equal size and more than 2 mm, sometimes 1 longer than 2 mm and 2 much shorter, sometimes all shorter than 2 mm; ovaries glabrous; styles with 2 branches, united at the base, stigmas plumose. Caryopses obovoid, with 3 smooth, longitudinal ribs at maturity, stylar bases 1–2 mm, persistent, sometimes eccentric; hila linear, about as long as the caryopses. x = unknown.

Amelichloa includes five species, four of which are South American. The fifth species, A. clandestina, grows in northern Mexico. Two species are established in the Flora region. A third species, A. caudata, was found on ballast dumps near Portland, Oregon, at the turn of the twentieth century; it is not established in the region.

Cattle avoid species of Amelichloa because of their sharply pointed leaves. This means that any of the species could become a serious problem in rangelands. Mowing favors their establishment and spread because it does not eliminate, and may disperse, the cleistogenes. The species are eaten by goats.

 

SELECTED REFERENCES Caro, J.A. and E. Sánchez. 1971. La identidad de Stipa brachychaeta Godron, S. caudata Trinius y S. bertrandii Philippi. Darwinia 16:637–653; Torres, M.A. 1993. Revisión del género Stipa (Poaceae) en la Provincia de Buenos Aires. Monografia 12. Comisión de Investigaciones Científicas, Provincia de Buenos Aires, La Plata, Argentina. 62 pp.

For an interactive dichotomous key, click here; the interactive, multientry key is not yet available.

1. Mature caryopses with inclined, eccentric stylar bases; lemmas glabrous or hairy between the lateral and marginal veins, glabrous between the midvein and the lateral vein, even at the base ... A. caudata
1. Mature caryopses with erect, usually centric stylar bases; proximal 1/2 of the lemmas pubescent between the lateral and marginal veins, at least initially, usually also between the midvein and lateral veins ... 2
2. Florets 4–5.5 mm long; ligules 0.2–0.6 mm long; anthers 2–3 mm long ... A. brachychaeta
2. Florets 5.5–8 mm long; ligules 0.5–1.5 mm long; anthers 3–4 mm long ... A. clandestina

 

1. Amelichloa brachychaeta (Godr.) Arriaga & Barkworth
Puna Needlegrass

Plants with knotty, shortly rhizomatous bases. Culms 40–90 cm tall, 1–2(3) mm thick, erect, glabrous; nodes usually 3. Basal sheaths mostly glabrous, margins ciliate distally; collars glabrous, often with tufts of hair to 1.5 mm on the sides; ligules 0.2–0.6 mm, mem-branous, strigose, ciliate, cilia to 2 mm, slightly longer at the leaf margins; blades 8–35 cm long, usually convolute and 0.5–0.8 mm in diameter, 2–3 mm wide when flat, erect, abaxial surfaces smooth, adaxial surfaces usually glabrous. Panicles 10–25 cm long, 1–4 cm wide, bases sometimes included in the upper leaf sheaths; branches ascending to spreading, longest lower branches 4–12 cm. Glumes subequal, 6–8 mm, linear-lanceolate, 1–3-veined, midveins smooth, scabridulous, or with stiff hairs, varying within a panicle, apices acuminate; florets 4–5.5 mm long, about 0.8 mm thick, fusiform; calluses 0.4–0.5 mm, blunt, strigose, hairs 0.5–0.8 mm; lemmas pubescent over and between the veins on the proximal 1/2, at least initially, hairs 0.5–0.8 mm, sometimes glabrous at maturity between the midveins and lateral veins, distal portion glabrous, tapering to the apices, apices with 0.7–1 mm hairs around the base of the awn; awns 10–18 mm, glabrous or scabrous, usually once-geniculate; paleas 3/4–9/10 as long as the lemmas, pubescent over the central portion, apices involute; lodicules 3; anthers 2–2.4(3) mm, penicillate. Caryopses 2–3 mm long, 0.9–1 mm thick, fusiform; style bases straight, centric. 2n = unknown.

Amelichloa brachychaeta has been found at a few locations in California, where it is listed as a noxious weed. It is native to Uruguay and Argentina. It is avoided by cattle because of its sharply pointed leaves. The cleistogamous panicles, which may be at or below ground level, remain a source of seeds unless the plants are completely uprooted. Amelichloa caudata and A. clandestina are a greater problem in this regard, because they appear to produce such panicles more frequently.

 

2. Amelichloa caudata (Trin.) Arriaga & Barkworth
South American Needlegrass

Plants cespitose, with knotty, rhizomatous bases. Culms 40–100 cm tall, 0.8–3(4.8) thick, erect, glabrous; nodes usually 3. Basal sheaths mostly glabrous, margins ciliate distally; collars glabrous, often with tufts of hair to 1.5 mm on the margins; ligules 0.2–0.6 mm, membranous, ciliate, cilia 1–2 mm, longest at the margins; blades 25–70 cm long, 2–7 mm wide when flat, usually convolute and 0.4–0.8 mm in diameter, erect, abaxial surfaces smooth, adaxial surfaces mostly glabrous. Panicles 10–45 cm long, 2–8 cm wide, bases sometimes included in the upper leaf sheaths; branches ascending to spreading, longest lower branches 4–12 cm. Glumes subequal, 5–11 mm, linear-lanceolate, 3-veined, midveins smooth, scabrous, or with stiff hairs, varying within a panicle, apices acuminate; florets 3.5–5(7) mm long, about 0.8 mm thick, fusiform; calluses 0.5–1 mm, blunt, strigose, hairs 0.5–0.8 mm; lemmas hairy over the veins, hairs 0.5–0.8 mm, glabrous between the mid- and lateral veins, glabrous or hairy between the lateral and marginal veins, distal portion glabrous, tapering to the apices, apices with 0.7–1 mm hairs around the base of the awn; awns 12–25 mm, glabrous or scabrous, once- or twice-geniculate; paleas 3.5–6.5 mm, 3/4–9/10 as long as the lemmas, pubescent over the central portion, apices involute; lodicules 3; anthers 2–4 mm in chasmogamous florets, cleistogamous florets sometimes with anthers of 2 lengths, about 0.4 mm and 0.7 mm, or all anthers of the same length, the long anthers penicillate. Caryopses about 3 mm long, 1–1.4 mm thick; style bases inclined, eccentric. 2n = unknown.

Amelichloa caudata is native to South America, extending from central Chile to Uruguay and Argentina. It was collected, as Stipa litoralis Phil., on ballast dumps near Portland, Oregon, early in the twentieth century. Although it has not become established in the Flora region, it has done so in Australia. It is a potentially invasive weed. Species with anthers of three different lengths, and of two lengths within a floret, have been reported for Nassella; it appears to be the first report of this pattern in the species of Amelichloa.

 

3. Amelichloa clandestina (Hack.) Arriaga & Barkworth
Mexican Needlegrass

Plants cespitose, with knotty, rhizomatous bases. Culms 50–90 cm tall, 1–2.9 thick, erect, glabrous; nodes usually 3. Sheaths mostly glabrous, margins ciliate distally; collars glabrous, often with tufts of hair to 1.5 mm on the margins; ligules 0.5–1.5 mm, membranous, ciliate, cilia 1–2 mm, slightly longer at the leaf margins; blades 10–50 cm long, usually tightly convolute and 0.4–1 mm in diameter, 2–4 mm wide when flat, erect, abaxial surfaces smooth, adaxial surfaces usually glabrous. Panicles 10–20 cm long, 1–5 cm wide, bases sometimes included in the leaf sheaths; branches ascending to spreading, longest lower branches 4–12 cm. Glumes subequal, 6.3–13 mm, linear-lanceolate, 3-veined, midveins smooth, scabrous, or with stiff hairs, varying within a panicle, apices acuminate; florets 5.5–8 mm long, about 0.8–1.3 mm thick, fusiform; calluses 0.3–0.6 mm, blunt, strigose, hairs 0.5–0.8 mm; lemmas pubescent on the proximal 1/2, the pubescence over the midvein extending to the awn, hairs 0.5–0.8 mm, distal portion glabrous, tapering to the apices, apices with 0.7–1 mm hairs around the base of the awn; awns 11–23 mm, glabrous or scabrous, usually twice-geniculate; paleas 3.5–6.5 mm, 3/4–9/10 as long as the lemmas, pubescent over the central portion, apices involute; lodicules 3; anthers 3–4 mm, penicillate. Caryopses about 3 mm long, 1–1.4 mm thick; style bases upright, centric. 2n = unknown.

Amelichloa clandestina is native from northern Mexico to Colombia. It has been accidentally introduced to pastures and roadsides in Texas, and is now established there. Reports from California need to be checked. They may reflect misidentifications of A. brachychaeta, which differs from A. clandestina in its shorter ligules, florets, and anthers.