Poaceae tribe Stipeae
Nassella
nassella, needlegrass, tussockgrass
annual or perennial, not woody, branches 1 to many at the upper nodes.
10-175(210) cm, sometimes branched at the upper nodes, branches flexible;
prophylls not evident, shorter than the sheaths.
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, not overwintering;
sheaths open;
cleistogenes sometimes present;
auricles absent;
ligules membranous, sometimes pubescent or ciliate;
blades of basal leaves 3-60 cm long, 0.2-8 mm wide, apices narrowly acute to acute, not sharp, flag leaf blades 1-80 mm, bases about as wide as the top of the sheaths.
usually terminal panicles, occasionally reduced to racemes in depauperate plants, sometimes 2-3 panicles developing from the highest cauline node.
terminal panicles, sometimes partially included at maturity.
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.
3-22 mm, with 1 floret;
rachillas not prolonged beyond the base of the floret;
disarticulation above the glumes, beneath the floret.
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.
longer than the floret, narrowly lanceolate or ovate, basal portion usually purplish at anthesis, color fading with age, (1)3-5-veined, sometimes awned;
florets usually terete, sometimes slightly laterally compressed;
calluses blunt or sharp, glabrous or antrorsely strigose;
lemmas usually papillose or tuberculate, at least distally, sometimes smooth throughout, glabrous or variously hairy, strongly convolute, wrapping 1.2-1.5 times around the caryopses, apices not lobed, fused distally into crowns, these often evident by their pale color and constricted bases;
crowns mostly glabrous, rims often bearing hairs with bulbous bases;
awns terminal, centric or eccentric, deciduous or persistent, usually twice-geniculate, second geniculation often obscure;
paleas up to 1/2 as long as the lemmas, glabrous, without veins, flat;
lodicules 2 or 3, if 3, the third somewhat shorter than the other 2;
anthers 1 or 3, if 3, often of 2 lengths, penicillate;
ovaries glabrous;
styles 2, bases free.
ovoid to fusiform, not beaked, pericarp thin;
hila linear;
embryos less than 1/3 the length of the caryopses.
glabrous, not ribbed;
hila elongate;
embryos to 2/5 as long as the caryopses.
= 7, 8, 10, 11, 12.
= 7, 8.
Poaceae tribe Stipeae
Nassella
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.)
Nassella used to be interpreted as a South American genus of approximately 14 species. It is now interpreted as including at least 116 species (Barkworth and Torres 2001), the majority of which are South American. The additional species were previously included in Stipa. There are eight species in the Flora region, one of which is introduced; two additional species treated here were found in the region at one time, but have not become established. The strongly convolute lemmas distinguish Nassella from all other genera of Stipeae in the Americas and, in combination with the reduced, ecostate, glabrous paleas, from all other genera in the tribe worldwide. Molecular data (Jacobs et al. 2006) support the expanded interpretation of Nassella. Relationships among the species have not been explored.
Many species of Nassella develop both cleistogamous and chasmogamous florets in the terminal panicle. The cleistogamous florets have 1-3 anthers that are less than 1 mm long; the chasmogamous florets have 3 anthers that are significantly longer. In addition, some species develop panicles in the axils of their basal sheaths. Spikelets of cleistogenes have reduced or no glumes, and florets with no or very short awns.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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. Florets 1.5-3 mm long; blades 0.2-1.5 mm wide, usually tightly convolute. | → 2 |
2. Florets widest about midlength; awns 45-100 mm long, almost centric | N. tenuissima |
2. Florets widest near the top; awns 7-35 mm long, eccentric. | → 3 |
3. Awns 15-35 mm long; lemmas strongly tuberculate, particularly distally | N. trichotoma |
3. Awns 7-10 mm long; lemmas smooth | N. chilensis |
1. Florets 3.4-13 mm long; blades 0.4-8 mm wide, flat to convolute. | → 4 |
4. Terminal segment of the awns cernuous. | → 5 |
5. Awns 12-55 mm long, 0.1-0.2 mm thick at the base | N. lepida |
5. Awns 50-110 mm long, 0.2-0.3 mm thick at the base | N. cemua |
4. Terminal segment of the awns straight. | → 6 |
6. Florets 3.4-5.5 mm long; lemmas not constricted below the crown; awns 19-32 mm long | N. viridula |
6. Florets 6-13 mm long; lemmas constricted below the crown; awns 30-120 mm long. | → 7 |
7. Lemmas hairy between the veins at maturity | N. pulchra |
7. Lemmas glabrous between the veins at maturity. | → 8 |
8. Crowns usually wider than long, the rims with hairs to 0.5 mm long; florets widest just below the crowns | N. neesiana |
8. Crowns usually longer than wide, the rims with hairs 1-2 mm long; florets widest near or slightly above midlength. | → 9 |
9. Florets 6.5-13 mm long; crowns often flaring distally; plants native to Texas and adjacent states | N. leucotricha |
9. Florets 6-8 mm long; crowns more or less straight-sided; plants introduced, established in California | N. manicata |
OR
WA
Flora NW
IL Wildflowers
KS Wildflowers
LA Plants
MN Wildflowers
PNW Herbaria
WildflowerSearch
iNaturalist
USDA Plants Database
