Flora of North America species comparison

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Poaceae tribe Stipeae

Amelichloa

needlegrass
Habit Plants usually perennial; usually tightly to loosely cespitose, sometimes rhizomatous. Plants perennial; cespitose.
Culms

annual or perennial, not woody, branches 1 to many at the upper nodes.

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

basally concentrated to evenly distributed;

sheaths open, margins not fused, sometimes ciliate distally, basal sheaths sometimes concealing axillary panicles (cleistogenes), sometimes wider than the blade;

collars sometimes with tufts of hair at the sides extending to the top of the sheaths;

auricles absent;

ligules scarious, often ciliate, cilia usually shorter than the base, ligules of the lower and upper cauline leaves sometimes differing in size and vestiture;

pseudopetioles absent;

blades linear to narrowly lanceolate, venation parallel, cross venation not evident, cross sections non-Kranz, without arm or fusoid cells;

epidermes of adaxial surfaces sometimes with unicellular microhairs, cells not papillate.

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

usually terminal panicles, occasionally reduced to racemes in depauperate plants, sometimes 2-3 panicles developing from the highest cauline node.

panicles, the main panicle terminal, apparently wholly chasmogamous.
Spikelets

usually with 1 floret, sometimes with 2-6 florets, laterally compressed to terete;

rachillas not prolonged beyond the base of the floret in spikelets with 1 floret, prolonged beyond the base of the distal floret in spikelets with 2-6 florets, prolongation hairy, hairs 2-3 mm;

disarticulation above the glumes and beneath the florets.

with 1 floret;

disarticulation above the glumes, beneath the floret.
Glumes

usually exceeding the floret(s), always longer than 1/4 the length of the adjacent floret, 1-10-veined, narrowly lanceolate to ovate, hyaline or membranous, flexible;

florets usually terete, sometimes laterally or dorsally compressed;

calluses usually well-developed, rounded or blunt to sharply pointed, often antrorsely strigose;

lemmas lanceolate, rectangular, or ovate, membranous to coriaceous or indurate, 3-5-veined, veins inconspicuous, apices entire, bilobed, or bifid, awned, lemma-awn junction usually conspicuous, awns 0.3-30 cm, not branched, usually terminal and centric or eccentric, sometimes subterminal, caducous to persistent, not or once- to twice-geniculate, if geniculate, proximal segment(s) twisted, distal segment straight, flexuous, or curled, not or scarcely twisted;

lodicules 2 or 3;

anthers 1 or 3, sometimes differing in length within a floret;

ovaries glabrous throughout or pubescent distally;

styles 2(3-4)-branched.

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

ovoid to fusiform, not beaked, pericarp thin;

hila linear;

embryos less than 1/3 the length of the 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

= 7, 8, 10, 11, 12.

= unknown.

Poaceae tribe Stipeae

Amelichloa
Distribution
[BONAP county map]
Discussion

The tribe Stipeae includes about 15 genera and approximately 500 species. It grows in Africa, Australia, South and North America, and Eurasia. In Australia, South America, and Asia, it is often the dominant grass tribe over substantial areas. It is not present in southern India, and is represented by only one native species in southern Africa. Most species grow in arid or seasonally arid, temperate regions.

Morphological considerations have led to the Stipeae being placed in three different subfamilies (Pooideae, Bambusoideae, and Arundinoideae) in the past, and even to recognition as a subfamily. Molecular data support its treatment as an early diverging lineage within the Pooideae (Soreng and Davis 1998; Grass Phylogeny Working Group 2001) that is more closely related to the Meliceae than the core pooid tribes.

Decker (1964) suggested including Ampelodesmos in the Stipeae on the basis of the cross sectional anatomy of its leaf blades. His suggestion is supported, not always strongly, by molecular studies (Soreng and Davis 1998; Grass Phylogeny Working Group 2001; Jacobs et al. 2006). The usual alternative is to treat Ampelodesmos as the only genus of a closely related, monospecific tribe, the Ampelodesmeae (Conert) Tutin, because it is so distinct from other members of the Stipeae, being, for example, the only member of the tribe with more than 1 floret in its spikelets and rachillas that are prolonged beyond the base of the terminal floret in a spikelet.

The lowest chromosome number known in the Stipeae is 2n =18 (Prokudin et al. 1977), suggesting that all members of the tribe are ancient polyploids. The wide range of base numbers listed is based on numbers for the various genera. The primary basic chromosome number for the tribe is probably 5 or 6, with higher numbers reflecting ancient euploidy.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

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.

(Discussion copyrighted by Flora of North America; reprinted with permission.)
Key
1. Spikelets with 2-6 florets
Ampelodesmos
1. Spikelets with 1 floret.
→ 2
2. Paleas sulcate, longer than the lemmas; lemma margins involute, fitting into the paleal groove; lemma apices not lobed
Piptochaetium
2. Paleas flat, from shorter than to longer than the lemmas; lemma margins convolute or not overlapping; lemma apices often lobed or bifid.
→ 3
3. Prophylls exceeding the leaf sheaths; plants cultivated as ornamentals.
→ 4
4. Panicles contracted; lemma awns once-geniculate
Macrochloa
4. Panicles open; lemma awns twice-geniculate
Celtica
3. Prophylls concealed by the leaf sheaths; plants native, introduced, sometimes cultivated as ornamentals.
→ 5
5. Flag leaf blades up to 12 mm long; basal leaves overwintering
Oryzopsis
5. Flag leaf blades more than 10 mm long; basal leaves not overwintering.
→ 6
6. Plants with multiple stiff branches from the upper nodes; pedicels sometimes plumose; species cultivated as ornamentals in the Flora region
Austrostipa
6. Plants not branching at the upper nodes, or with a few, flexible branches; pedicels never plumose; species native, established introductions, or cultivated as ornamentals.
→ 7
7. Apices of the leaf blades sharp and stiff; caryopses obovoid, often with 3 smooth ribs at maturity; cleistogenes usually present
Amelichloa
7. Apices of the leaf blades acute to acuminate, never both sharp and stiff; caryopses fusiform, ovoid or obovoid, without ribs; cleistogenes sometimes present.
→ 8
8. Lemma margins strongly overlapping their whole length at maturity, lemma bodies usually rough throughout, apices not lobed; paleas 1/4 - 1/2 the length of the lemmas, without veins, glabrous
Nassella
8. Lemma margins usually not or only slightly overlapping for some or all of their length at maturity, strongly overlapping in some species with smooth lemmas, lemma bodies usually smooth on the lower portion, apices often 1-2-lobed; paleas from 1/3 as long as to equaling or slightly exceeding the lemmas, 2-veined at least on the lower portion, usually with hairs or both lemmas and paleas glabrous.
→ 9
9. Calluses 1.5-6 mm long, sharply pointed; plants perennial or annual, if perennial, awns 65-500 mm long, if annual, awns 50-100 mm long; panicle branches straight.
→ 10
10. Lower ligules densely hairy, upper ligules less densely hairy or glabrous; plants perennial
Jarava
10. Ligules glabrous or inconspicuously pubescent, lower and upper ligules alike in vestiture; plants perennial or annual.
→ 11
11. Plants perennial; florets 7-25 mm long; awns scabrous or pilose on the first 2 segments, the terminal segment scabrous, or if pilose, the hairs 1-3 mm long
Hesperostipa
11. Plants annual or perennial, if annual, the florets 4-7 mm long and the awns not plumose, if perennial, the florets 18-27 mm long and the awns plumose on the terminal segment, the hairs 5-6 mm long
Stipa
9. Calluses 0.1-2 mm long, blunt to sharply pointed; plants perennial; awns 1-70 mm; panicle branches straight or flexuous.
→ 12
12. Florets usually dorsally compressed at maturity, sometimes terete; paleas as long as or longer than the lemmas and similar in texture and pubescence; lemma margins separate for their whole length at maturity
Piptatherum
12. Florets terete or laterally compressed at maturity; paleas often shorter than the lemmas, sometimes less pubescent, sometimes as long as the lemmas and similar in texture and pubescence; lemma margins often overlapping for part or all of their length at maturity.
→ 13
13. Glumes without evident venation, glume apices rounded to acute; plants subalpine to alpine, sometimes growing in bogs
Ptilagrostis
13. Glumes with 1-3(5) evident veins or the glume apices attenuate; plants growing from near sea level to subalpine or alpine habitats, not growing in bogs.
→ 14
14. Lemma bodies with evenly distributed hairs of similar length or completely glabrous, sometimes with longer hairs around the base of the awn; basal segment of the awns sometimes with hairs up to 2 mm long
Achnatherum
14. Lemma bodies with hairs to 1 mm long over most of their length, with strongly divergent hairs 3-8 mm long on the distal 1/4, or the basal segment of the awns with hairs 3-8 mm long
Jarava
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
Source FNA vol. 24, p. 109. Author: Mary E. Barkworth;. FNA vol. 24, p. 181. Author: Mirta O. Arriaga;.
Parent taxa Poaceae > subfam. Pooideae Poaceae > subfam. Pooideae > tribe Stipeae
Subordinate taxa
Achnatherum, Amelichloa, Ampelodesmos, Austrostipa, Celtica, Hesperostipa, Jarava, Macrochloa, Nassella, Oryzopsis, Piptatherum, Piptochaetium, Ptilagrostis, Stipa
A. brachychaeta, A. caudata, A. clandestina
Name authority Dumort. Arriaga & Barkworth
Web links 
Unless otherwise noted, all data comes from the online version of the Flora of North America, who have made most of their content available via a Creative Commons license (CC BY 4.0).



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