Nassella E.Desv.
Last edited
June 13, 2003
[This page is part of a series that seeks to summarize the Stipeae, as I see the tribe.  It is modified at very irregular intervals.  Mary E. Barkworth]

CONTENTS: History, Characteristics, Synopsis, Formal generic description; recent paper (provides more information and summaries of distribution)

HISTORY
Nassella
used to be treated as a South American genus with about 12 species Parodi (1947). Thomasson (1976) pointed out that many American species traditionally included in Stipa sensu lato shared a number of unusual characteristics with the species of Nassella. In 1990,
Barkworth formally expanded it to a genus of more than 70 species.  Torres (1997) has expanded it still further, describing a number of new species from northwestern Argentina and transferring several that Barkworth (1990) omitted. The synopsis below includes all the species recognized in Barkworth and Torres ().   

The author of Nassella is Emile Desvaux, not the older N.A. Desvaux.  Authors of Plant Names recommends that Emile Desvaux be abbreviated as E. Desv., the abbreviation Desv. being kept for the older person.  

Nassella remains a primarily South American genus, with the greatest concentration of species being in northwestern Argentina, Bolivia, and northern Chile.   

CHARACTERISTICS (For a more formal description, click here)
The characteristics that unite the species included in Nassella sensu lato are:

  • Lemma usually gray-brown rather than chestnut brown
  • Lemma convolute, the outer margin overlapping the inner margin and extending 1/3-2/3 of the way around it
  • Lemma apex solid, often differing from the body of the lemma in being smooth and cream-colored
  • Lemma apex often bearing bulbous-based hairs, these sometimes fused together to form a distinct crown
  • Palea 1/3 the length of the lemma or shorter, usually glabrous, without veins
  • Lemma epidermis with extremely short fundamental cells
  • Epiblast as long as the embryonic coleoptile, possibly hooded (closer study of many more species needed)

The difference between the two groups of species was that those placed in Nassella had short, tubby florets with a short, often eccentric awn that is often deciduous whereas those placed in Stipa had larger, elongate florets with long awns.  Parodi (1944) suggested, in a discussion of a similar situation in Piptochaetium, that they were adaptations to different dispersal mechanisms. Barkworth (1990) suggested that these two sets of characteristics reflect adaptation to different habitats.

Barkworth (1990) suggested that Nassella is most closely related to Hesperostipa and Piptochaetium, but Thomasson (pers. comm.) believes it to be more closely related to Achnatherum. The limited DNA data available (Hsiao, unpublished) support Thomasson.

For reasons reviewed in Barkworth (1990), the authority for Nassella is Desvaux and the type species is Nassella pungens Desvaux.

Synopsis of the genus
The table below lists the taxa in Nassella in alphabetical order. It is taken from Taxon ??:??-?? but includes publication information for all the names involved.  

Nassella airoides (E. Ekman) Barkworth , Taxon 39(4):609 (1990). Basionym: Stipa airoides E. Ekman  (1912). Isotypes: BAA! ex S; CORD! Torres.

Nassella ancoraimensis F. Rojas , Gayana, Bot. 54(2):165, Iam. 4 (1997, printed 1998).

Nassella arcaensis (Speg.) Torres , Monogr. Comis. Invest. Ci. Prov. Buenos Aires 13:13 (1997). Basionym: Stipa arcaensis Speg.  (1901). Lectotype: LP! ex LPS 2457 Torres.

Nassella arcuata (R. E. Fries) Torres , Monogr. Comis. Invest. Ci. Prov. Buenos Aires13:13 (1997). Basionym: Stipa arcuata R. E. Fries  (1905). Isotype: CORD! Torres.

Nassella arechavaletae (Speg.) Barkworth , Taxon 39(4):609 (1990). Basionym: Stipa arechavaletae Speg.  (1901). Syntype: LP! ex LPS 2456; Isotype: BAA! Torres.

Nassella argentinensis (Speg.) Peñailillo , Gayana, Bot. 55:998 (1998, printed May 1999). Basionym: Stipa argentinenis Speg.  (1901). Holotype: LP! ex 2458; Torres.

Nassella asplundii Hitchc., Contr. U.S. Natl. Herb. 24(8):394 (1927). Holotype: US! Torres.

Nassella ayacuchensis (Tovar) Barkworth, Taxon 39(4):609 (1990). Basionym: Stipa ayacuchensis Tovar  (1988).

Nassella brachychaetoides (Speg.) Barkworth , Taxon 39(4):609 (1990). Basionym: Stipa brachychaetoides Speg.  (1925). Holotype: LP! ex LPS 2459; Isotype: BAA! Torres.

Nassella brachyphylla (Hitchc.) Barkworth , Taxon 39(4):609 (1990). Basionym: Stipa brachyphylla Hitchc.  (1925). Holotype: US! Torres.

Nassella brasiliensis (A. Zanín & Longhi-Wagner) Peñailillo , Gayana, Bot. 55:998 (1998, printed May 1999). Basionym: Stipa brasiliensis A. Zanín & Longhi-Wagner  (1990).

Nassella cabrerae Torres , Monogr. Comis. Invest. Ci. Prov. Buenos Aires 13:14, f. 1 (1997). Holotype: LP! Torres.

Nassella caespitosa Griseb. , Abh. Königl. Ges. Wiss. Göttingen 19:258 (1874).
Synonyms: Stipa caespitosa (Griseb.) Speg.  (1901); Stipa caespitosa var. subtypica Speg.  (1901), nom. inval.; Stipa plagiostephana Speg.  (April, 1925); Stipa violacea Hitchc.  (November, 1925). Isotypes: BAA! CORD! Torres.

Nassella carettei (Hauman) Torres , Monogr. Comis. Invest. Ci. Prov. Buenos Aires 13:16 (1997). Basionym: Stipa carettei Hauman  (1917). Syntype: BAA Col. Typus 2998! Torres.

Nassella catamarcensis Torres , Monogr. Comis. Invest. Ci. Prov. Buenos Aires 13:17, f. 2 (1997). Holotype: BAA! Torres.

Nassella cernua (Stebbins & Love) Barkworth , Taxon 39(4):609 (1990). Basionym: Stipa cernua Stebbins & Love  (1941). Holotype: UC 641631! Barkworth.

Nassella chaparensis F. Rojas , Gayana, Bot. 54(2):167, Iam. 6 (1997, printed 1998).

Nassella charruana (Arechav.) Barkworth , Taxon 39(4):609 (1990). Basionym: Stipa charruana Arechav. (1895).
Synonym: Stipa longicylindrica Kuntze  (1898).
Note: Introduced to Australia (Jacobs et al. 1998).

Nassella chilensis (Trin.) E. Desv.  in Gay, Fl. Chil. 6:265 (1853). Basionym: Urachne chilensis Trin.  (1834). Probable Isotype: BAA! Bertero 1173 ex P; Torres.

Nassella clarazii (Ball) Barkworth , Taxon 39(4):609 (1990). Basionym: Stipa clarazii Ball  (1884). Type fragment: BAA! Torres.
Synonyms: Stipa quadrifaria Kuntze  (1898); Stipa clarazii var. bulbosa Speg.  (1901).

Nassella coquimbensis (Matthei) Peñailillo , Gayana, Bot. 55:998 (1998, printed May 1999). Basionym: Stipa coquimbensis Matthei  (1965).

Nassella cordobensis (Speg.) Barkworth , Taxon 39(4):609 (1990). Basionym: Stipa cordobensis Speg.  (1901). Lectotype: LP! ex LPS 2451; Syntype: LP! ex LPS 2451; Torres.
Synonyms: Stipa tenuis var. papillosa Hack.  in Stuck. (1911); Stipa papillosa (Hack.) Hitchc.  (1925); Stipa cordobensis var. tuberculata F. A. Roig  (1964).

Nassella crassiflora (Roseng. & B. R. Arill.) Barkworth , Taxon 39(4):609 (1990). Basionym: Stipa crassiflora Roseng. & B. R. Arill.  (1964). Isotype: BAA! Torres.

Nassella curamalalensis (Speg.) Barkworth , Taxon 39(4):609 (1990). Basionym: Stipa curamalalensis Speg.  (1901). Holotype: LP! ex LPS 2455; Torres.
Synonym: Stipa tenuissima var. curamalalensis (Speg.) Hack.  in Stuck. (1911).

Nassella curviseta (Hitchc.) Barkworth , Taxon 39(4):609 (1990). Basionym: Stipa curviseta Hitchc.  (1925). Type: US 1099338! Torres.

Nassella dasycarpa (Hitchc.) Torres , Monogr. Comis. Invest. Ci. Prov. Buenos Aires 13:19 (1997). Basionym: Stipa dasycarpa Hitchc.  (1925). Holotype: US 1099337! Torres.

Nassella depauperata (Pilg.) Barkworth , Taxon 39(4):609 (1990). Basionym: Stipa depauperata Pilg.  (1920). Isotype: BAA! Torres.
Synonym: Stipa leptothera var. atroviolacea Hack.  Type: W! Torres.

Nassella duriuscula (Phil.) Barkworth , Taxon 39(4):609 (1990). Basionym: Stipa duriuscula Phil.  (1864). Type fragment: BAA Col. Typus 3037! ex SGO; Torres.

Nassella elata (Speg.) Torres , Monogr. Comis. Invest. Ci. Prov. Buenos Aires 13:20 (1997). Basionym: Stipa caespitosa var. elata Speg.  (1901). Holotype: LP! ex LPS 12524; Torres.

Nassella entrerriensis (Burkart) Peñailillo , Gayana, Bot. 55:998 (1998, printed May 1999). Basionym: Stipa entrerriensis Burkart  (1968). Holotype: SI! Torres.

Nassella fabrisii Torres , Monogr. Comis. Invest. Ci. Prov. Buenos Aires 13:20, f. 2 (1997). Holotype: LP! Torres.

Nassella famatinensis Torres , Monogr. Comis. Invest. Ci. Prov. Buenos Aires 13:21, f. 1 (1997). Holotype: BAA! Torres.

Nassella filiculmis (Delile) Barkworth , Taxon 39(4):609 (1990). Basionym: Stipa filiculmis Delile (1849).
Note: Introduced to the south of France, probably in wool (Thellung 1912).

Nassella formicarum (Delile) Barkworth , Taxon 39(4):609 (1990). Basionym: Stipa formicarum Delile (1849). Type fragment: BAA! ex Herb. Monpellier; Torres.
Note: Introduced to the south of France, probably in wool (Thellung 1912).

Nassella gibba (Phil.) M. Muñoz , Gayana, Bot. 47(1-2):26 (1990). Basionym: Piptochaetium gibbum Phil.  (1896).
Synonym: Nassella exserta var. asperata Parodi  (1947), fide Muñoz-Schick (1990).

Nassella gigantea (Steud.) M. Muñoz , Gayana, Bot. 47(1-2):23 (1990). Basionym: Urachne gigantea Steud.  (1854).
Synonyms: Nassella exserta Phil.  (1865); Nassella melanocarpa Phil.  (1873); Nassella fuscescens Phil.  (1896); Nassella pugae Phil. (1896), fide Muñoz-Schick (1990).

Nassella glabripoda Torres , Monogr. Comis. Invest. Ci. Prov. Buenos Aires 13:22, f. 1 (1997). Holotype: LIL 14901! Isotype: BAA! Torres.

Nassella hirtifolia (Hitchc.) Barkworth , Taxon 39(4):610 (1990). Basionym: Stipa hirtifolia Hitchc.  (1925).

Nassella holwayii (Hitchc.) Barkworth , Taxon 39(4):610 (1990). Basionym: Stipa holwayii Hitchc.  (1925). Paratype fragment: BAA Col. Typus 4166! Torres.

Nassella huallancaensis (Tovar) Barkworth , Taxon 39(4):610 (1990). Basionym: Stipa huallancaensis Tovar  (1985).

Nassella hunzikeri (Caro) Barkworth , Taxon 39(4):610 (1990). Basionym: Stipa hunzikeri Caro  (1966). Holotype: CORD! Torres.

Nassella hyalina (Nees) Barkworth , Taxon 39(4):610 (1990). Basionym: Stipa hyalina Nees  (1829). Type fragment: BAA! ex B; Torres.
Note: Introduced to New South Wales, Australia (Vickery et al. 1986; Jacobs et al. 1998).

Nassella ibarrensis (Kunth) Laegaard , Novon 8:23-30 (1998). Basionym: Stipa ibarrensis Kunth   (1816). Holotype: P! Torres.
Note: Peñailillo published this combination in Gayana, Bot. 55:86, but the volume was not published until May, 1999, so Laegaard's publication, which was published in 1998, has priority.

Nassella inconspicua (J. Presl) Barkworth , Taxon 39(4):610 (1990). Basionym: Stipa inconspicua J. Presl  in C. Presl (1830). Type fragment: BAA Col. Typus 3099! Torres.

Nassella juergensii (Hack.) Barkworth , Taxon 39(4):610 (1990). Basionym: Stipa juergensii Hack.  (1909). Type fragment: BAA Col. Typus 3108! Torres.

Nassella juncea Phil. , Linnaea 33:277 (1865).
Synonym: Nassella chilensis var. juncea (Phil.) M. Muñoz  (1990).

Nassella lachnophylla (Trin.) Barkworth , Taxon 39(4):610 (1990). Basionym: Stipa lachnophylla Trin.  (1836).

Nassella laevissima (Phil.) Barkworth , Taxon 39(4):610 (1990). Basionym: Piptochaetium laevissimum Phil.  (1864).
Synonyms: Stipa laevissima (Phil.) Speg.  (1901); Stipa breviculmis Hitchc.  (1925); Stipa lahittei Parodi  (1938).

Nassella lepida (Hitchc.) Barkworth , Taxon 39(4):610 (1990). Basionym: Stipa lepida Hitchc.  (1915). Holotype: US 733683! Barkworth.

Nassella leptocoronata (Roseng. & B. R. Arill.) Barkworth , Taxon 39(4):610 (1990). Basionym: Stipa leptocoronata Roseng. & B. R. Arill.  (1964). Isotype: BAA! ex MVFA 2145; Torres.

Nassella leptothera (Speg.) Torres , Monogr. Comis. Invest. Ci. Prov. Buenos Aires 13:25 (1997). Basionym: Stipa leptothera Speg.  (1901). Lectotype: LP! ex LPS 12642; Torres.

Nassella leucotricha (Trin. & Rupr.) R. W. Pohl in Barkworth, Taxon 39(4):610 (1990). Basionym: Stipa leucotricha Trin. & Rupr.  (1842).
Note: Recorded as being introduced into Australia (Vickery et al. 1986).

Nassella linearifolia (E. Fourn.) R. W. Pohl, Fieldiana, Bot., n.s., 4:336 (1980). Basionym: Stipa linearifolia E. Fourn.  (1886).
Synonyms: Oryzopsis florulenta Pilg. (1899); Stipa florulenta (Pilg.) Parodi (1944).

Nassella longicoronata (Roseng. & B. R. Arill.) Barkworth , Taxon 39(4):610 (1990). Basionym: Stipa longicoronata Roseng. & B. R. Arill.  (1964). Holotype fragment: SI! ex MVFA 2150; Torres

Nassella longiglumis (Phil.) Barkworth , Taxon 39(4):610 (1990). Basionym: Stipa longiglumis Phil.  (1864). Probable type fragment: SGO 45631! Torres.

Nassella macrathera (Phil.) Barkworth , Taxon 39(4):610 (1990). Basionym: Stipa macrathera Phil.  (1896). Probable isotype fragment: BAA Col. Typus 3130! ex SGO; Torres.

Nassella manicata (E. Desv.) Barkworth , Taxon 39(4):610 (1990). Basionym: Stipa manicata E. Desv.  in Gay (1853). Type fragment: BAA Col. Typus 3135! ex P; Torres.
Note: Introduced and established in California in areas associated with sheep grazing; misidentified as N. formicarum  by Barkworth (1993b).

Nassella megapotamica (Spreng. ex Trin.) Barkworth , Taxon 39(4):610 (1990). Basionym: Stipa megapotamica Spreng. ex Trin.  (1830).
Synonyms: Stipa latifolia Hack. & Arechav.  (1895); Stipa latissimifolia Kuntze  (1898); Stipa manicata var. latifolia (Hack. & Arechav.) Speg.  (1901); Stipa manicata var. media Speg.  (1901).
Note: Established, but apparently not spreading, near Canberra, Australia (Jacobs & Everett 1993; Jacobs et al. 1998).

Nassella melanosperma (J. Presl) Barkworth , Taxon 39(4):610 (1990). Basionym: Stipa melanosperma J. Presl  in C. Presl (1830).
Synonyms: Stipa bonariensis Henrard & Parodi  (1926); Nassella bonariensis (Henrard & Parodi) Barkworth  (1990).

Nassella mexicana (Hitchc.) R. W. Pohl  in Barkworth, Taxon 39(4):611 (1990). Basionym: Stipa mexicana Hitchc.  (1925). Holotype: US 99386! Barkworth, Torres.

Nassella meyeniana (Trin. & Rupr.) Parodi , Darwinia 7:379, f. 5. (1947). Basionym: Urachne meyeniana Trin. & Rupr.  (1842).

Nassella meyeri Torres , Monogr. Comis. Invest. Ci. Prov. Buenos Aires 13:26, f. 2. (1997). Holotype: LIL! Isotype: BAA! Torres.

Nassella mucronata (Kunth) R. W. Pohl  in Barkworth, Taxon 39(4):611 (1990). Basionym: Stipa mucronata Kunth  in Humb., Bonpl. & Kunth (1816). Lectotype fragment: US 294533! ex P; Torres.
Synonyms: Stipa grisebachii E. Fourn.  (1886); Stipa setigera J. Presl  in C. Presl (1830); Stipa trochlearis Nees & Meyen  (1841).
Note: Introduced to Coimbra, Portugal and Aranjuez, Spain (Vázquez & Devesa 1996), France (Kerguélen 1975; Martinovsky 1980), and Italy (Martinovsky 1980; Pignatti 1982; Moraldo 1986).

Nassella nardoides (Phil.) Barkworth , Taxon 39(4):611 (1990). Basionym: Danthonia nardoides Phil.  (1891). Isotype: BAA! Torres.
Synonyms: Stipa calchaquia Speg.  (1901); Stipa nardoides (Phil.) Hack. ex Hitchc.  (1925).

Nassella neesiana (Trin. & Rupr.) Barkworth , Taxon 39(4):611 (1990). Basionym: Stipa neesiana Trin. & Rupr.  (1842).
Synonyms: Stipa eminens Nees  (1829), non Cav. (1799); Stipa neesiana var. glabrata Arechav.  (1896); Stipa setigera var. glabrata Arechav. ex Speg.  (1901); Stipa setigera var. hispidula Speg.  (1901).
Note: Introduced into southern France (Thellung 1912), New South Wales and Victoria, Australia (Vickery et al. 1986; Jacobs & Everett 1993, 1996); and New Zealand (Jacobs et al. 1989; Connor et al. 1993; Edgar & Connor 2000).

Nassella nidulans (Mez) Barkworth , Taxon 39(4):611 (1990). Basionym: Stipa nidulans Mez  (1921). Isotype: CORD! Torres.

Nassella niduloides (Caro) Barkworth , Taxon 39(4):611 (1990). Basionym: Stipa niduloides Caro  (1966). Holotype: CORD! Torres.

Nassella novarae Torres , Monogr. Comis. Invest. Ci. Prov. Buenos Aires 13:29, f. 2 (1997). Holotype: LP! Torres.

Nassella nubicola (Speg.) Torres , Monogr. Comis. Invest. Ci. Prov. Buenos Aires 13:30 (1997). Basionym: Stipa nubicola Speg.  (1901). Lectotype: LP! ex LPS 2426; Torres.

Nassella nutans (Hack.) Barkworth , Taxon 39(4):611 (1990). Basionym: Stipa nutans Hack.  (1909). Holotype fragment BAA Col. Typus 3184! ex US; Torres.

Nassella pampagrandensis (Speg.) Barkworth , Taxon 39(4):611 (1990). Basionym: Stipa pampagrandensis Speg.  (1901). Lectotype: LP ex LPS 2419! Torres.

Nassella pampeana (Speg.) Barkworth , Taxon 39(4):611 (1990). Basionym: Stipa pampeana Speg.  (1901). Holotype: LP! ex LPS 2420; Isotype: BAA! Torres.

Nassella paramilloensis (Speg.) Torres , Monogr. Comis. Invest. Ci. Prov. Buenos Aires 13:31 (1997). Basionym: Stipa paramilloensis Speg.  (1901). Lectotype: LP! ex LPS 2422; Torres.

Nassella parodii (Matthei) Barkworth , Taxon 39(4):611 (1990). Basionym: Stipa parodii Matthei  (1965).

Nassella parva Torres , Monogr. Comis. Invest. Ci. Prov. Buenos Aires 13:32, f. 1 (1997). Holotype: LIL! Torres.

Nassella pauciciliata (Roseng. & Izag.) Barkworth , Taxon 39(4):611 (1990). Basionym: Stipa megapotamica var. pauciciliata Roseng. & Izag.  (1961). Isotype: BAA Col. Typus 3162! Torres.

Nassella pfisteri (Matthei) Barkworth , Taxon 39(4):611 (1990). Basionym: Stipa pfisteri Matthei  (1965).

Nassella philippii (Steud.) Barkworth , Taxon 39(4):611 (1990). Basionym: Stipa philippii Steud.  (1854). Type fragment: BAA Col. Typus 3214! Torres.

Nassella planaltina (A. Zanín & Longhi-Wagner) Peñailillo , Gayana, Bot. 55:998 (1998, printed May 1999). Basionym: Stipa planaltina A. Zanín & Longhi-Wagner  (1990). Paratype: UTC 219007! Barkworth, Torres.

Nassella poeppigiana (Trin. & Rupr.) Barkworth , Taxon 39(4):611 (1990). Basionym: Stipa poeppigiana Trin. & Rupr.  (1842).
Synonyms: Stipa amethystina Steud.  (1854); Stipa manicata var. typica Speg.  (1901), nom. inval.; Stipa latifolia var. grandiflora Hack.  in Stuck. (1911); Stipa megapotamica var. latiflora Roseng. & Izag.  (1961).

Nassella pseudopampagrandensis (Caro) Barkworth , Taxon 39(4):611 (1990). Basionym: Stipa pseudopampagrandensis Caro  (1966). Syntype: CORD! ex Herb. Stuckert 16804; Torres.

Nassella psittacorum (Speg.) Peñailillo , Gayana, Bot. 55:998 (1998, printed May 1999). Basionym: Stipa psittacorum Speg.  (1901). Holotype: LP! ex LPS 2445; Torres.

Nassella pubiflora (Trin. & Rupr.) E. Desv.  in Gay, Fl. Chil. 6:264 (1853). Basionym: Urachne pubiflora Trin. & Rupr.  (1842).
Synonyms: Oryzopsis pubiflora (Trin. & Rupr.) Scribn.  (1893); Nassella flaccidula Hack.  (1908); Nassella corniculata Hack.  (1908); Nassella deltoidea Hack.  (1912); Stipa pubiflora (Trin. & Rupr.) M. Muñoz  (1990).

Nassella pulchra ((Hitchc.) Barkworth , Taxon 39(4):611 (1990). Basionym: Stipa pulchra Hitchc.  (1915). Holotype: US 416590! Barkworth.

Nassella punensis Torres , Monogr. Comis. Invest. Ci. Prov. Buenos Aires 13:35, f. 1 (1997). Holotype: LP! Isotype: BAA! Torres

Nassella pungens E. Desv.  in Gay, Fl. Chil. 6:268 (1853); Atlas (Iam. 75, f. 1) (1854).
Synonyms: Nassella humilis Phil.  (1865); Nassella johnstonii Parodi  (1947).

Nassella ragonesei Torres , Monogr. Comis. Invest. Ci. Prov. Buenos Aires 13:35, f. 2 (1997). Holotype: BAA! Torres.

Nassella rhizomata (A. Zanín & Longhi-Wagner) Peñailillo , Gayana, Bot. 55:998 (1998, printed May 1999). Basionym: Stipa rhizomata A. Zanín & Longhi-Wagner  (1990). Paratype: UTC 2190006! Barkworth, Torres.

Nassella rosengurttii (Chase) Barkworth , Taxon 39(4):611 (1990). Basionym: Stipa rosengurttii Chase  (1943). Isotype: BAA Col. Typus 3234! Torres.

Nassella rupestris (Phil.) Torres , Monogr. Comis. Invest. Ci. Prov. Buenos Aires 13:36 (1997). Basionym: Stipa rupestris Phil.  (1891). Type: SGO 63159! Torres.

Nassella sanluisensis (Speg.) Barkworth , Taxon 39(4):611 (1990). Basionym: Stipa sanluisensis Speg.  (1901). Lectotype: LP ex LPS 12646! Torres.
Synonyms: Stipa debilis Mez  (1921); Stipa debilis var. papillosa Caro  (1966); Stipa sanluisensis var. longispicula Caro  (1966).

Nassella sellowiana (Nees ex Trin. & Rupr.) Peñailillo , Gayana, Bot. 55:998 (1998, printed May 1999). Basionym: Stipa sellowiana Nees ex Trin. & Rupr.  (1842). Type fragment: BAA Col. Typus 3254! ex B; Torres.
Synonym: Stipa molfinoi Speg.  (1925), fide Zuloaga et al. (1994).

Nassella smithii (Hitchc.) Barkworth , Taxon 39(4):612 (1990). Basionym: Stipa smithii Hitchc.  (1930). Holotype: US 1357804! Torres.

Nassella soukupii (Tovar) Barkworth, Taxon 39(4):612 (1990). Basionym: Stipa soukupii Tovar  (1988). Isoype: LP! Torres.

Nassella spegazzinii (Arechav.) Barkworth, Taxon 39(4):612 (1990). Basionym: Stipa spegazzinii Arechav.  (1903).
Synonym: Stipa uruguaycola Speg.  (1925), fide Burkart (1969), Rosengurtt et al. (1970).

Nassella stuckertii (Hack.) Barkworth , Taxon 39(4):612 (1990). Basionym: Stipa stuckertii Hack.  in Stuck. (1911). Isotype: CORD! Torres.

Nassella subnitida (Roseng. & B. R. Arill.) Barkworth , Taxon 39(4):612 (1990). Basionym: Stipa subnitida Roseng. & B. R. Arill.  (1964). Isotype: BAA Col. Typus 3276! Torres.

Nassella tenuiculmis (Hack.) Peñailillo , Gayana, Bot. 55:998 (1998, printed May 1999). Basionym: Stipa tenuiculmis Hack. (1915).

Nassella tenuis (Phil.) Barkworth , Taxon 39(4):612 (1990). Basionym: Stipa tenuis Phil.  (1870).
Synonyms: Stipa argentina Speg.  (1898); Stipa tenuis var. argentina (Speg.) Speg.  (1901); Stipa puelches Speg.  (1925). Type fragment: LP! ex LPS; Torres.

Nassella tenuissima (Trin.) Barkworth , Taxon 39(4):612 (1990). Basionym: Stipa tenuissima Trin.  (1836).
Synonyms: Stipa oreophila Speg.  (1896); Stipa tenuissima var. oreophila (Speg.) Speg.  (1901); Stipa tenuissima var. planicola Speg.  (1898).
Note: Introduced to Australia (Jacobs et al. 1998), New Zealand (Ford 1994; Connor & Ford 1996; Gardner et al. 1996), and South Africa (Connor & Ford 1996). Cultivated in California (Barkworth, pers. obs.), and New Zealand (Connor & Ford 1996; Edgar & Connor 2000).

Nassella torquata (Speg.) Barkworth , Taxon 39(4):612 (1990). Basionym: Stipa torquata Speg.  (1901). Holotype: LP! ex LPS 2429; Torres.

Nassella trachyphylla Henrard , Meded. Rijks-Herb. 40:57 (1921).

Nassella trichotoma (Nees) Hack. ex Arechav. , Anales Mus Nac. Montevideo 1:276, f. 19 (1894). Basionym: Stipa trichotoma Nees  (1829). Type fragment: BAA Col. Typus 3292! ex B; Torres.
Synonyms: Urachne trichotoma (Nees) Trin.  (1834); Piptochaetium trichotomum (Nees) Griseb.  (1879); Oryzopsis trichotoma (Nees) Druce  (1910).
Note: Introduced to southern France and Italy (Burkart 1969); Australia and New Zealand (Vickery & Jacobs 1980; Jacobs & Everett 1993, 1996; Jacobs et al. 1989; Edgar & Connor 2000); and the U.S. (U.S.D.A.-A.P.H.I.S. 1990). So far as is known, all populations of the species have been eliminated from the continental U.S. The U.S. Department of Agriculture regards the species as one of the ten worst potential weeds for U.S. agriculture.

Nassella tucumana (Parodi) Torres , Monogr. Comis. Invest. Ci. Prov. Buenos Aires 13:38 (1997). Basionym: Stipa tucumana Parodi  (1948). Holotype: BAA! Torres.
Synonym: Nassella asperifolia F. Rojas , Gayana, Bot. 54(2):166, Iam. 5 (1997, printed 1998). Isotype: UTC 203411! Barkworth, Torres.

Nassella uspallatensis (Speg.) Torres , Monogr. Comis. Invest. Ci. Prov. Buenos Aires 13:38 (1997). Basionym: Stipa uspallatensis Speg.  (1901). Syntype: LP! ex LPS 12649; Torres.

Nassella vallsii (A. Zanín & Longhi-Wagner) Peñailillo , Gayana, Bot. 55:998 (1998, printed May 1999). Basionym: Stipa vallsii A. Zanín & Longhi-Wagner  (1990). Paratype: UTC 219008! Barkworth, Torres.

Nassella ventanicola (Cabrera & Torres) Barkworth , Taxon 39(4):612 (1990). Basionym: Stipa ventanicola Cabrera & Torres  (1968). Holotype: LP! Torres.

Nassella viridula (Trin.) Barkworth , Taxon 39(4):612 (1990). Basionym: Stipa viridula Trin.  (1836). Holotype: LE! Barkworth.

Nassella wurdackii (Tovar) Barkworth , Taxon 39(4):612 (1990). Basionym: Stipa wurdackii Tovar  (1981).

Nassella yaviensis Torres , Monogr. Comis. Invest. Ci. Prov. Buenos Aires 13:39, f. 2 (1997). Holotype: LP! Torres.

Excluded species

Nassella barrancaensis (F. A. Roig) Barkworth , Taxon 39(4):609 (1990). Basionym: Stipa barrancaensis F. A. Roig  (1966).

 More Formal Generic Description
Plants perennial, cespitose; basal branching intra- or extravaginal. Culms branching above the base in some species. Sheaths open; auricles absent; ligules membranous, sometimes pubescent or ciliate. Inflorescence an open or closed panicle, sometimes not fully exserted at maturity. Spikelets with 1 floret and no rachilla extension. Glumes longer than the anthoecium, with (1)3-5 veins, usually long-tapering to an acuminate tip, frequently purplish at the base before drying out; callus well-developed, short and blunt to long and sharp, glabrous or antrorsely strigose; lemma strongly convolute, coriaceous, with a crown at the apex, this varying from inconspicuous to conspicuous; pappus absent; awn centric or eccentric, scabrous, caducous or persistent, varying from short to long, from non-geniculate and only slightly twisted to twice-geniculate with a strongly twisted column; palea up to 1/3 the length of the lemma, almost always glabrous and without veins; lodicules 2 or 3, if 3, the third somewhat shorter than the other two; style branches 2, not united at the base; anthers 1 or 3, when 3, often of two different lengths.

The morphological feature that best distinguishes Nassella from other species of Stipeae is its strongly convolute lemma. It is also the most useful field character. The extent of the overlap is 25-50%, the outer margin of the lemma usually lying over the lateral vein of the inner half of the lemma, sometimes extending to the midvein of the lemma. This extended overlap, combined with the coriaceous texture of the lemma, makes it very difficult to open the floret to observe the palea or caryopsis. It is, however, possible to pinch off the callus with one's fingernails or strong tweezers in such a way that the palea and flower remain attached to it and available for observation in the field. Other characters supporting the new generic boundary are those italicized in the above description, plus the lemma epidermal pattern (Thomasson 1976, 1978, 1979; Barkworth 1990; Torres 1997), and ITS sequence data (Jacobs et al. 2000).

The only other stipoid genus in which some species have strongly convolute, coriaceous lemmas is the Australian endemic Austrostipa. They do not, however, have the reduced, glabrous, unveined palea that occurs in almost all species of Nassella, nor the distinctive lemma epidermal pattern (Thomasson 1976, 1978, 1979; Barkworth & Everett 1987), nor similar ITS sequences (Jacobs et al. 2000).