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A synopsis of Digitaria (Paniceae, Panicoideae, Poaceae) in Mexico, including the new species Digitaria michoacanensis.

The genus Digitaria Heller (subfamily Panicoideae Link, tribe Paniceae R. Br., subtribe Anthephorinae Benth.) is a worldwide and morphologically diverse assemblage primarily found in tropical to warm temperate regions (Clayton and Renvoize, 1986; Vega et al., 2009). It is economically important because some species are used as forage and several others are noxious weeds (Henrard, 1950; Veldkamp, 1973). The genus is characterized by having cartilaginous, glabrous fertile lemmas with membranous margins, and due to the great morphological variation among the species, some authors have divided it into several subgenera and sections (e.g., Henrard, 1950; Veldkamp, 1973; Rugolo de Agrasar 1974; Clayton and Renvoize, 1986). One of the most comprehensive and complete studies of Digitaria was done by Henrard (1950), who studied all known species and classified them into four subgenera, one of them, Digitaria subgen. Digitaria (as Eudigitaria (Stapf) Hernrard, nom. inval)), with 32 sections. Other authors have rearranged this classification by merging several sections (e.g., Veldkamp, 1973; Rugolo de Agrasar, 1974; Clayton and Renvoize, 1986). In the most recent study, Vega et al. (2009) tested Henrard's classification with a cladistic analysis using morphological traits. Their results did not support the infrageneric classification and only a few of Henrard's sections received some support as monophyletic groups.

With 230 species worlwide, Digitaria is the second largest genus in the tribe Paniceae, after Paspalum L. (Clayton et al., 2006 onwards; Vega et al., 2009; Sanchez-Ken, 2010). Beetle et al. (1987) reported 21 species for Mexico, Davila et al. (2006) cited 26, whereas Zuloaga et al. (2003) reported 27. The database of the Global Biodiversity Information Facility (http://data.gbif.org/) contains more than 58 species names for Mexico, many of them probably erroneously identified. According to Henrard's (1950) classification, the subgenera Leptoloma (Chase) Henrard and 11 sections of subg. Digitaria are present in Mexico. When using other classifications, the number of sections in the country decreases to eight, seven and three following Veldkamp (1973), Rugolo de Agrasar (1974), and Clayton and Renvoize (1986), respectively.

As a result of the revision of the genus Digitaria for Flora del Bajio y Regiones Adyacentes (Sanchez-Ken, in prep.), I propose a new species that is described and illustrated here. I also provide a synopsis, including a key, of the genus in Mexico.

MATERIALS AND METHODS

Several important Mexican grass collections were studied (ENCB, IEB, and MEXU). A preliminary list of names was taken from The Global Biodiversity Information Facility (GBIF, www.gbif.org), which includes the UNIBIO database (Unidad de Informatica para la Biodiversidad of the Instituto de Biologia, UNAM, http:// unibio.ibiologia.unam.mx); and the Catalogue of the New World Grasses (http://mobot.mobot.org/W3T/Search/nwgc.html). To verify the identity of the species, online databases from NY, MO, P, and US were also consulted, including images of types and representative specimens as available (acronyms according to Index Herbariorum, http://sciweb.nybg.org/science2/IndexHerbariorum.asp). Fertile florets of the newly proposed species were coated with gold and photographed using a (JEOL-JSM-5310LV) scanning electron microscope.

RESULTS

Digitaria michoacanensis Sanchez-Ken sp. nov. Figs. 1, 2.

Plants perennial, tufted, caespitose, with a knotty rhizomatous base, the rhizomes short and thin; culms 15-30(-55) cm tall; nodes 2-3, branching below, puberulent to scabrellous; internodes short covered by the sheaths, glabrous, puberulent to shortly hirtellous near the nodes; leaves basal, sheaths 3-4(7) cm long, longer than the internodes, the upper with a reduced blade below the synflorescence, the lowermost purple and short-hirsute, the next green and glabrous, margins shortpilose; ligules 0.3-0.6 mm long, membranous, hyaline to brown, glabrous, erose; auricles formed at the apex of the sheath, short and usually fused to the ligule; blades 3.2-5.7(-10) cm long, 3-6 mm wide, lanceolate, flat, thick slightly sclerophyllous, base slightly rounded to subcordate, adaxially sparsely long-pilose, the hairs up to 4 mm long, more abundant toward the ligular area, abaxially glabrous, margins scabrellous, apex acute; synflorescence with 2(-3) racemes, digitately inserted or on a short axis about 1 cm long; racemes 2-6.5 cm long, equal or unequal, appressed; peduncle glabrous, sparsely puberulent below the base of the synflorescence; pulvinus puberulent to hirtellous; rachis 0.4-0.5 mm wide, triquetrous, the sides narrower than the midvein, scabrous to scabrellous; pedicels 1-4.5 mm long, hirtellous, mostly toward the apex, apex discoid; spikelets 2.6-2.7 mm long, 1.3-1.4 mm wide, elliptic, usually in groups of threes up to the middle of the raceme, paired and solitary toward the apex, apex acute-apiculate, densely brown pilose, the hairs up to 0.4 mm long, clavate, with bulbous, truncate to rounded tips, ascending and appressed; first glume 0.3-0.5 mm long including the hairs, hyaline, truncate, lobed or somewhat acute, veinless, pilose, the hairs clavate, brown, with bulbous apices that are truncate or slightly rounded, the hairs exceeding the glume apex and longer than the hairs of the sterile lemma; second glume 2-2.7 mm long including the hairs, 0.9-1 mm wide, 3-5-veined, densely pilose in the spaces between the veins, veins glabrous, the hairs clavate, brown, with bulbous apices that are truncate or slightly rounded; sterile lemma slightly shorter than the spikelet, leaving free the apex of the fertile floret, 5-veined, the veins unequally spaced, sometimes the outer ones reduced, densely pilose in the spaces between the veins, the hairs clavate, brown, with bulbous apices that are truncate or slightly rounded; sterile palea minute; lodicules fused; fertile lemma, 2.6-2.7 mm long, 1-1.1 mm wide, slightly ovate, slightly acuminate-acute, light to dark brown, finely papillose-striate, margins hyaline over the palea, apex pale to white; fertile palea similar in texture to the fertile lemma; stamens 3, anthers 1.3-1.4 mm long; caryopsis not seen.

[FIGURE 1 OMITTED]

[FIGURE 2 OMITTED]

Micromorphology. SEM images clearly show that the glumes and sterile lemma are densely pilose with long clavate macrohairs which have a bulbous truncate or slightly rounded tip (Fig. 2 E-H). Some hairs appear flattened and this might be due to dehydration. The hairs of the first glume are longer than the hairs on the fertile or sterile florets. The fertile lemma epidermis has long cells that are much wider than long, with strongly sinuous walls, and there is a single papilla with a smooth surface.

Type: Mexico. Michoacan, municipio de Tingambato, Llano de Cananguio, al NE de Pichataro, pastizal secundario, 2600 m, 31.VIII.1989, H. Diaz Barriga y E. Perez 5930 (holotype: IEB).

Paratypes. Mexico. Estado de Mexico. Por la carretera de Villa Victoria a El Oro, zacatonal de Muhlenbergia y Festuca, 2570 m, 9.VIII.1981, R. Guzman & P. Guerrero 4251 (MEXU). Michoacan, municipio de Quiroga, Cerro Azul, al N de Quiroga, vegetacion secundaria derivada de bosque de pino-encino, 2420 m, 23.VII.1980, J. Caballero y C. Mapes 1190 (MEXU); 14 km S of the junction of hwys 15 and 37 at Carapan, 2070 m, 20.VIII.1975, oak-pine forest, G. Davidse & J. Davidse 9904 (MO).

Distribution, habitat and phenology. This new species is restricted to Mexico in the states of Michoacan and Mexico, the type from El Bajio region. The habitat is grassland or transition to pine-oak forest, at elevations between 2,070 to 2,600 m. Flowering and fruiting occur in July and August.
Key to the Mexican species of Digitaria

1 Spikelets in groups of three or more at least
  in the middle of the raceme or branch.
  2 Sterile lemma and second glume glabrous.
    3 Plants annual; spikelets 1.6-2 mm long         D. filiformis
                                                        var. laeviglu-
                                                        mis
    3 Plants perennial; spikelets 2.3-2.4 mm         D. bakeri
      long
  2 Sterile lemma and second glume pilose,
    or at least one of them with some
    hairs on the apex or margins.
    4 Hairs of the spikelet bracts brown.            D. badia
      5 Spikelets 2.3-2.6 mm long, 1-1.1 mm wide;
        first glume glabrous; sterile lemma
        7-veined; anthers 1-1.1 mm long
      5 Spikelets 2.6-2.7 mm long, 1.3-1.4 mm        D. michoacanensis
        wide; first glume pilose; sterile lemma
        5-veined; anthers 1.3-1.4 mm long
    4 Hairs of the spikelet bracts white or
      yellowish.
      6 Rachis winged; hairs of the spikelet         D. violascens
        bracts with verrucose walls
      6 Rachis triquetrous; hairs of the             D. argillacea
        spikelet bracts with smooth walls.
        7 Hairs of the sterile lemma of two
          types, the first type yellow to gold,
          glassy, setaceous with an acute apex,
          up to 0.8 mm long, mixed with the
          second type which are shorter, whitish
          and more delicate with bulbous tips
        7 Hairs of the sterile lemma of one
          kind with bulbous tips.
          8 Second glume and sterile lemma           D. paniculata
            7-veined
          8 Second glume 0-3-veined; sterile
            lemma 5-7-veined.
            9 Second glume up to 0.5 mm long,
              less than half the length of the
              spikelet, 0-veined.
              10 Spikelets 1.3-1.5 mm long;          D. curtigluma
                 plants annual; anthers ca. 0.5
                 mm long ... D. breedlovei
              10 Spikelets 1.8-2.7 mm long;
                 plants perennial; anthers 1.3-
                 1.5 mm long
            9 Second glume 0.5-0.8 mm long,
              more than half the length of the
              spikelets, if less, then 3-veined.
              11 Second glume half the length        D. bakeri
                 of the spikelets, with some hairs
                 toward the apex; plants perennial;
                 sterile lemma 7-veined
              11 Second glume more than half
                 the length to as long as the
                 spikelets, pilose; plants annual
                 or perennial; sterile lemma
                 5-7-veined.
                 12 Fertile lemma 1.4-1.9 mm         D. filiformis
                    long; anthers 0.3-0.5 mm long;      var. filifor-
                    plants annual                       mis
                 12 Fertile lemma 1.9-2.5 mm
                    long; anthers 0.8-1.1 mm long;
                    plants annual or perennial.
                    13 Plants annual; spikelets      D. ternata
                       elliptic, with base and apex
                       rounded
                    13 Plants perennial;
                       spikelets ovate-lanceolate,
                       with base and apex attenuate.
                       14 Ligule 0.6-0.8 mm long;    D. leucocoma
                          blades up to 9(13) cm long;
                          plants geniculate at the
                          base
                       14 Ligule 1.3-2.6 mm long;
                          blades 15-25 cm long;
                          plants erect
1 Spikelets paired or solitary.
  15 Synflorescence an open panicle;
     spikelets long pedicellate.
     16 Spikelets 2.3-3.3 mm long;                   D. pubiflora
        second glume 3-veined
     16 Spikelets 3.5-4.6 mm long;                   D. arenicola
        second glume 5-7-veined
  15 Synflorescence a raceme;
     spikelets short pedicellate.
     17 Spikelets of the pair dimorphic              D. bicornis
     17 Spikelets of the pair homomorphic.
        18 Sterile lemma veins equidistant.
           19 First glume a minute rim less          D. velutina
              than 0.1 mm long or wanting;
              spikelets 1.5-2 mm long; sterile
              lemma 7-veined
           19 First glume triangular or ovate,
              0.3-1 mm long; spikelets 2.5-5 mm
              long; sterile lemma 5-veined.
              20 Spikelets 4-5 mm long; spaces       D. sellowii
                 between the veins of sterile lemma
                 glabrous; sterile lemma hairs long,
                 usually yellow, sometimes whitish
              20 Spikelets 2.5-3.1 mm long;          D. hitchcockii
                 spaces between the veins of the
                 sterile lemma pilose; sterile lemma
                 hairs short, white to purple
        18 Sterile lemma central veins distant
           to each other, leaving wide intervening
           spaces.
           21 Sterile lemma scabrous or
              scabrellous on the central or
              lateral veins.
              22 Spaces between the veins of         D. sanguinalis
                 the sterile lemmas glabrous;
                 central veins glabrous, only the
                 lateral veins scabrellous above
                 the middle; plants annual
              22 Spaces between the lateral
                 veins of the sterile lemmas
                 pilose; central veins scabrous
                 or scabrellous from the base to
                 the apex or only above the
                 middle, sometimes just few
                 prickles toward the apex seen
                 with high magnification; plants
                 perennial.
                 23 Racemes whorled or more          D. milanjiana
                    commonly along the axis;
                    ligule eciliate
                 23 Racemes on a short axis,         D. eriantha
                    several whorls; ligule
                    ciliate
           21 Sterile lemma with glabrous
              veins.
              24 Sterile lemma hairs
                 1.5-6 mm long.
                 25 Space between the                D. insularis
                    central veins of the
                    sterile lemma pilose;
                    hairs of the sides of
                    the central veins yellow
                    to whitish
                 25 Space between the
                    central veins of the
                    sterile lemma glabrous;
                    hairs of the sides of
                    the central veins white
                    to purplish.
                    26 Racemes stiffly               D. patens
                       ascending or spreading;
                       terminal pedicels
                       of the racemes more
                       than 7.4 mm long
                    26 Racemes appressed             D. californica
                       to the axis; terminal
                       pedicels of the racemes
                       less than 7 mm long
              24 Sterile lemma hairs up
                 to 1 mm long.
                 27 Sterile lemmas                   D. abyssinica
                    glabrous or with
                    sparse and minute
                    hairs at the margins
                 27 Sterile lemmas
                    pilose between the
                    veins toward the
                    sides and margins.
                    28 Second glume
                       nearly as long as
                       the spikelet.
                       29 Sterile lemma              D. leucites
                          hairs 0.5-0.6 mm
                          long
                       29 Sterile lemma              D. texana
                          hairs 0.1-0.3 mm
                          long
                    28 Second glume up
                       to a third as long
                       as the spikelet.
                       30 Rachis of the              D. horizontalis
                          racemes with very
                          few long hairs,
                          usually in the
                          lower half
                       30 Rachis of the
                          racemes without
                          long hairs.
                          31 First glume             D. ciliaris
                             triangular to
                             ovate, 0.2-0.8
                             mm long; sterile
                             lemma hairs
                             0.5-1 mm long;
                             second glume
                             (1.2-) 1.5-2.7
                              mm long
                          31 First glume             D. setigera
                             wanting or a
                             truncate rim up
                             to 0.1 mm long;
                             sterile lemma
                             hairs 0.1-0.2
                             mm long; second
                             glume 0.5-1.3
                             mm long


DISCUSSION

The new species belongs to the 'group Ternata of Digitaria sections Calvulae (Stapf) Henrard or Leianthae Henrard (Henrard, 1950), These sections were merged into the section Phaeotrichae Rugolo (Rugolo de Agrasar, 1974), section Filiformis (Honda) Veldkamp (Veldkamp, 1973) or section Ischaemum Ohwi (Clayton and Renvoize, 1986). However, the monophyly of these taxa has not been tested. The inclusion of the new species into the Ternata is based on the morphological similarity shared with D. badia.

The new species is allied to D. badia, with which it is morphologically similar. Both species possess the same type of pubescence on the spikelet bracts, which consists of brown, capitate or clavate hairs. Also, both species share brown fertile florets, a perennial habit with knotty rhizomes, and synflorescences with 2 or 3(-5) racemes. However, there are vegetative and reproductive characters that separate these species (Table 1). Vegetatively, the plants of D. badia are taller, with long internodes, and have leaves that are normally caulinar with blades up to 20 cm long, whereas plants of D. michoacanensis are smaller with short, reduced internodes, and have basal leaves up to 10 cm long. In D. badia there are usually (2-)3-4(-5) racemes and the spikelets are smaller and narrower; in contrast in the new species there are only 2(-3) racemes, and the spikelets are larger. The first glume of D. badia is clearly glabrous (Fig. 2A), but it is pilose in D. michoacanensis (Fig. 2E). The hairs of D. badia (Fig. 2B) are slender and longer than in the new species, and the tip is apiculate or pointed. In D. michoacanensis the hairs (Fig. 2F) are thick and stout with the tip truncate or rounded, or clavate and calvous according to the terminology of Veldkamp (1973). The fertile lemma of D. michoacanensis (Fig. 2G) is slightly ovate, contrary to the narrowly elliptic fertile lemmas of D. badia (Fig. 2C).

Other species from Digitaria section Clavipilae (Stapf) Henrard from South America that might be related to the new species are D. atra Luces and D. killenii A.S. Vega & Rugolo (Vega and Rugolo de Agrasar, 2001, 2002), but these have shorter hairs.

Thirty-one species and two varieties of Digitaria are now documented as occurring in Mexico. A similar number is present in North America, north of Mexico (Wipff, 2003) and Central America (Vega and Rugolo de Agrasar, 2007) with 31 and 30 species respectively. Of the 31 species in Mexico, four are endemic, and when compared to other regions,22 are shared between Canada/U. S. A. and Mexico (endemic, cultivated, and weeds), from which five are restricted to the United States and Mexico. Seventeen species are shared with Central America and six species are widely distributed from Mexico to Central and South America. Of the 31 species, eight are introduced weeds and are distributed worldwide. Regarding the diversity of the genus by state in Mexico, the five richest states are Jalisco with 18 spp., Oaxaca and Veracruz with 17 spp., Chiapas with 16 spp., and Michoacan with 13 spp. A similar pattern of diversity distribution occurs with the genera Paspalum and Urochloa P. Beauv. (Sanchez-Ken, 2010, 2011).

The Global Biodiversity Information Facility website contains as many as 58 names within the genus for Mexico, which includes valid names, synonyms and invalid names. Some of these names belong to cultivated species that do not have Mexican collections represented in herbaria examined (e.g., D. ischaemum (Schreb.) Muhl., D. natalensis Stent, and D. smutsii Stent). There are several morphologically similar and not well understood species of annuals that form a complex related to D. filiformis. One of them, Digitaria curvinervis, is cited for Durango and Sonora in the GBIF database; however, the same specimen is cited as D. panicea (Sw.) Urb. by Herrera (2001). According to McVaugh (1983), D. panicea is a Caribbean species and may represent a form of D. filiformis; D. curvinervis could also represent a form of D. filiformis. Wipff (1996) made two combinations D. filiformis var. dolichophylla (Henrard) Wipff and D. filiformis var. laeviglumis (Fernald) Wipff that he applied to taxa restricted to North America (Wipff, 2003) north of Mexico. In Mexico, after reviewing the scarce material of D. filiformis, I found a herbarium sheet from Oaxaca, with two specimens, one with glabrous spikelets and the other with pilose spikelets. The specimen with glabrous spikelets belongs to D. filiformis var. laeviglumis and the second to the typical variety. According to Wipff (2003), the typical variety was the only one that extended into Mexico, but based on my observations D. filiformis var. laeviglumis can no longer be considered endemic to the United States. Furthermore, there are other specimens that appear morphologically similar to D. filiformis var. dolichophylla by having glabrous basal sheaths. However, the Mexican specimens have much wider blades, and I retain these specimens under the typical variety until further investigation. Digitaria ischaemum, a European weed, is cited from Coahuila, Durango, Sonora, and Tamaulipas from two specimens deposited in ANSM, ARIZ, and US that I was not able to verify.

The citation of D. longiflora for Mexico was an error listed in TROPICOS (www.tropicos.org) since the specimen was collected in Costa Rica; this has since been corrected. Two other species D. natalensis and D. smutsii were cited from specimens of the Banco Nacional de Germoplasma of the Universidad Autonoma de Chapingo, and it is possible that these species were grown from seed and tested for forage.

Digitaria eriantha Steud., or under the names of D. pentzii Stent, D. eriantha subsp. pentzii (Stent) Kok or D. decumbens Stent., has been cited as a cultivar for several states; however, after reviewing all available material only one specimen in the herbarium collection fits the description of the species. The rest of the specimens belonged mostly to D. bicornis (Lam.) Roem. & Schult. and D. ciliaris (Retz.) Koeler. It seems possible that most of the specimens identified as D. pentzii var. minor were used to include the species in Las Gramineas de Mexico (Beetle et al., 1987).

Digitaria leucocoma (Nash) Urb. has been treated as a synonym of D. villosa (Walter) Pers. by several authors (Zuloaga et al., 2003; Soreng et al., 2003 and onwards); however, I agree with Hernard (1950) that these two species are distinct. The former is a tall perennial plant with long leaf blades and the second glume is shorter than the spikelet. In contrast D. villosa is a short perennial plant with short leaf blades and the second glume is nearly as long as the spikelet. The latter species once was treated as a variety of D. filiformis, a delicate annual (Soreng et al., 2003 and onwards). Henrard (1950) suggested that D. pilosa Michx. is a synonym of D. villosa because the small habit of the species; however, it is more similar to some forms of D. filiformis.

In a similar situation, I agree with Swallen (1953) that D. obtusa Swallen is a distinct species, although morphologically similar to D. leucocoma. In addition to the characters mentioned in the key, D. obtusa is shorter with short leaf blades and short racemes whereas D. leucocoma is taller with longer basal and caulinar leaf blades, and longer racemes. Therefore, it is possible that D. villosa does not occur in Mexico, and it is here excluded.

Finally, the separation of D. filiformis and D. cayoensis Swallen is often difficult. In the original description of D. cayoensis Swallen (1938) indicates that the sterile lemmas have 3 veins, and this feature was also mentioned in the Grasses of Guatemala (Swallen, 1955). Henrard (1950), Pohl and Davidse (1998), and Rugolo de Agrasar (Pers. comm.) indicate that the sterile lemmas have 5-7 veins which would match the description of D. filiformis. Therefore, I consider D. cayoensis a synonym of D. filiformis, although more study of these entities is needed.

SYNOPSIS OF THE SPECIES OF DIGITARIA OCCURRING IN MEXICO

Herbarium acronyms in parenthesis, according to Index Herbariorum (Thiers, B. (continuously updated). Index Herbariorum: A global directory of public herbaria and associated staff. New York Botanical Garden's Virtual Herbarium, http://sweetgum.nybg.org/ih/). (U.S.A. = United States of America, Ags. = Aguascalientes, B.C. = Baja California, B.C.S. = Baja California Sur, Camp. = Campeche, Coah. = Coahuila, Col. = Colima, Chih. = Chihuahua, Chis. = Chiapas, D.F. = Distrito Federal, Dgo. = Durango, Gro. = Guerrero, Gto. = Guanajuato, Hgo. = Hidalgo, Jal. = Jalisco, Mex. = Estado de Mexico, Mich. = Michoacan, Mor. = Morelos, N.L. = Nuevo Leon, Nay. = Nayarit, Oax. = Oaxaca, Pue. = Puebla, Q.R. = Quintana Roo, Qro. = Queretaro, S.L.P. = San Luis Potosi, Sin. = Sinaloa, Son. = Sonora, Tab. = Tabasco, Tamps. = Tamaulipas, Talx. = Tlaxcala, Ver. = Veracruz, Yuc. = Yucatan, Zac. = Zacatecas, C. Amer. = Central America, S. Amer. = South America, Car. = Caribbean, O. W. = Old World).

1. Digitaria abyssinica (Hochst. ex A. Rich.) Stapf, Bull. Misc. Inform. Kew 1907: 213. 1907. Panicum abyssinicum Hochst. ex A. Rich., Tent. Fl. Abyss. 2: 360-361. 1851. Type: Ethiopia, 22.IX.1837, W. Schimper 82 (holotype: P; isotypes: BR, K, L, US).

Distribution: U.S.A., Mexico (Ver.), C. Amer., S. Amer., O. W. Introduced, weed.

Reference: Veracruz: Mpio. Tlaquilpan, camino de terraceria entre Tequila y Tehuapan, 18.VI.1997, M. J. Lizama 878 (MEXU).

2. Digitaria arenicola (Swallen) Beetle, Leafl. W. Bot. 6(8): 162. 1951. Leptoloma arenicola Swallen, Tex. Res. Found. Contrib. 1: 1. 1950. Leptoloma cognatum (Shult.) Chase var. arenicola (Swallen) Gould, Southw. Naturalist 15: 391. 1971. Digitaria cognata (Schult.) Pil. var. arenicola (Swallen) R. Webster, Syst. Bot. 13(4): 594. 1988. Type: United Stated of America, Texas, Kennedy Co., 8 mi S of Sarita, 24.IV.1949, Swallen 10122 (holotype: US; isotypes: MO, US).

Distribution: United States of America, Mexico (Tamps.). Native.

Reference: Tamaulipas: Mpio. San Fernando, Barra de Catan, 18.III.1989, M. H. Cervera 518 (MEXU).

3. Digitaria argillacea (Hitchc. & Chase) Fernald, Rhodora 22(258): 104. 1920. Syntherisma argillaceum Hitchc. & Chase, Contr. U.S. Natl. Herb. 18(7): 296. 1917. Type: Puerto Rico, Monte Alegrillo, near Maricao, 20.X.1913, A. Chase 6221 (holotype: US; isotypes: L, NY).

Distribution: Mexico (Chis., Col., Dgo., Gto., Jal., Mex., Mich., Mor., Nay., Oax., Son.), C. Amer., S. Amer., Car. Native.

Reference: Oaxaca: San Isidro Monjas del Centro, 20.XI.1991, L. Garcia P. s.n. (MEXU).

4. Digitaria badia (Scribn. & Merr.) Fernald, Rhodora 22: 104: 1920. Panicum badium Scribn. & Merr., Bull. Div. Agrostol., U.S.D.A. 24: 12. 1901. Type: Mexico, Oaxaca, Sierra de San Felipe, 6.X.1894, C. L. Smith 915 (holotype: US; isotypes: MO, US).

Ditribution: Mexico (Chis., D. F., Gto., Hgo., Jal., Mex., Mich., Oax., Qro., Tlax., Zac.). Endemic.

Reference: Queretaro: Mpio. Amealco, El Asserin, 19.IX.1994, A. Avalos M. 94 (MEXU).

5. Digitaria bakeri (Nash) Fernald, Rhodora 22(258): 102. 1920. Syntherisma bakeri Nash, Bull. Torrey Bot. Club 25(6): 296. 1898. Type: United States of America, Florida, Grasmere, no date, C. H. Baker 47 (holotype: NY; isotype: US).

Distribution: U.S.A., Mexico (Chis., Ver.), C. Amer., S. Amer. Native.

Reference: Veracruz: La Barranca, carretera a Coscomatepec, 22.VII.1982, R. Guzman M., A. A. Beetle & E. Manrique 3855 (MEXU).

6. Digitaria bicornis (Lam.) Roem. & Schult., Syst. Veg. 2: 470. 1817. Panicum bicorne Lam., Tabl. Encycl. 1: 176. 1791. Type: Mauritius?, no date, T. F. W. Sieber 42 (holotype: P-LAM; isotype: US fragm. ex P-LAM).

Distribution: U.S.A., Mexico (B.C.S., Camp., Chis., Chih., Col., D. F., Gro., Hgo., Jal., Mex., Mich., Mor., Nay., N. L., Oax., Pue., Q. R., Qro., Sin., Son., Tab., Tamps., Ver., Yuc.), C. Amer., S. Amer., Car. Weed.

Reference: Michoacan: Mpio. Arteaga, N end of town, 8.V.2002, V. W. Steinmann, G. Puime & B. Vrskovy 2424 (MEXU).

7. Digitaria breedlovei R.W. Pohl & Davidse, Novon 2(2): 106. 1992. Type: Mexico, Chiapas, Mpio. de Villa Corzo, 65 km S of Mexican highway 190, on road from Tuxtla Gutierrez to Nueva Concordia, 12.IX.1974, D. E. Breedlove 37709 (holotype: MO; isotypes: CAS, MEXU).

Distribution: Mexico (Chis., Dgo.). Endemic.

Reference: Chiapas: Mpio. Tuxtla Gutierrez, Mexican highway 190, Nueva Concordia, 12.IX.1974, D. E. Breedlove 37709 (CAS, MEXU).

8. Digitaria californica (Benth.) Henrard, Blumea 1(1): 99. 1934. Panicum californicum Benth., Bot. Voy. Sulphur. 55-56. 1844. Type: Mexico: Baja California, Bay of Magdalena, in 1841, Hinds s.n., (holotype: K, isotype: US fragm. ex K).

Distribution: U. S. A., Mexico (Ags., B.C., B.C. Sur., Chih., Coah., Dgo., Gto., Hgo., Jal., N.L., Pue., Qro., S. L. P., Sin., Son., Tamps., Zac.), C. Amer., S. Amer. Native.

Reference: San Luis Potosi: Mpio. Matehuala, Ejido Calabacillas, 7.VIII.1986, H. Bravo M. 207 (MEXU).

9. Digitaria ciliaris (Retz.) Koeler, Descr. Gram. 27. 1802. Panicum ciliare Retz., Observ. Bot. 4: 16. 1786. Type: China: Guangzhou, no date, Wennerberg s.n. (lectotype: LD, designated by Blake, Roy. Soc, Queensland 81: 11. 1969).

Distribution: U. S. A., Mexico (Ags., B.C., B.C. Sur., Camp., Chih., Chis., Coah., Col., D.F., Dur., Gro., Gto., Hgo., Jal., Mex., Mich., Mor., Nay., N.L., Oax., Pue., Qro., Q.R., S.L.P., Sin., Son., Tab., Tamps., Ver., Yuc.), C. Amer., S. Amer, Car., O. W. Introduced, weed.

Reference: Queretaro: Mpio. Landa, alrededores de Puerto de Guadalupe, 10. XII.1996, L. G. Rincon N. 433 (MEXU).

10. Digitaria curtigluma Hitchc., Proc. Biol. Soc. Wash. 40: 84. 1927. Type: Panama: Chiriqui, El Boquete, 28.IX.1911, A.S. Hitchcock 8176 (holotype: US; isotypes: K, L, SI).

Distribution: Mexico (Chis., D.F., Gto., Jal., Mex., Mich., Oax., Pue.), C. Amer. Native.

Reference: Michoacan: Mpio. Patzcuaro, Estacion de Ajuno, 8.XI.1985, J. M. Escobedo 602 (IEB).

11. Digitaria eriantha Steud., Flora 12(2): 468-469. 1829. Type: South Africa; Cape of Good Hope, no date, von Ludwig s.n. (holotype: probably P).

Distribution: U.S.A., Mexico (Oax., Tamps., Ver., Zac.), C. Amer., S. Amer., O. W. Introduced, pasture.

Reference: Zacatecas: Mpio. Calera, Campo agricola experimental INIFAP, 20.X.1989, J. J. Balleza C. 2600 (MEXU).

12a. Digitaria filiformis (L.) Koeler var. filiformis Descr. Gram. 26: 1802. Panicum filiforme L., Sp. Pl. 1: 57. 1753. Type: United States of North America, no date, Kalm s.n. (lectotype: LINN-90.38, designated by Hitchcock, Contr. U. S. Natl. Herb. 12(3): 117. 1908).

Distribution: U.S.A., Mexico (Chih., Chis., Coah., D.F., Dgo., Gto., Jal., Mex., Mich., Nay., Oax., Son., Ver., Zac.), C. Amer., S. Amer, Car., O. W. Native.

Reference: Guanajuato: Mpio. Comonfort, Rancho Rinconcillo de los Remedios, 27.VII.1994, J. C. Castaneda L. 194 (MEXU).

12b. Digitaria filiformis (L.) Koeler var. laeviglumis (Fernald) Wipff, Phytologia 80(5): 348. 1996. Digitaria laeviglumis Fernald, Rhodora 22(258): 102. 1920. Type: United States of America: New Hampshire; Hillsborough Co., Manchester, 11.IX.1901, F.W. Batchelder s.n. (holotype: GH).

Distribution: U.S.A., Mexico (Oax.). Native.

Reference: Oaxaca: about 66 mi NW of Tehuantepec, 29.VIII.1953, J. R. Reeder & C. G. Reeder 2171 (MEXU).

13. Digitaria hitchcockii (Chase) Stuck., Annuaire Conserv. Jard. Bot. Geneve 17: 287. 1914. Valota hitchcockii Chase, Proc. Biol. Soc. Wash. 24: 110. 1911. Type: United States of America: Texas, San Antonio, 24.VI.1910, A.S. Hitchcock 5329 (holotype: US).

Distribution: U.S.A., Mexico (Coah., N.L., Oax., Qro., S.L.P., Tamps.). Native.

Reference: San Luis Potosi: in the valley of the Rio Verde and in the Sierra de Cuates, along the route Rio Verde-San Francisco-Patros-Cardunes Rayon, 14.IX.1954, E. R. Sohns 1299 (MEXU).

14. Digitaria horizontalis Willd., Enum. Pl. 1: 92. 1809. Type: Dominican Republic; Santo Domingo, no date, Anon. s.n. (holotype: B-W; isotypes; MVFA, US).

Distribution: U.S.A., Mexico (Chis., Coah., Col., Gro., Jal., Mex., Mich., Mor., Nay., N.L., Oax., Pue., Q.R., S.L.P., Sin., Son., Tab., Tamps., Ver., Yuc.), C. Amer., S. Amer, Car. Weed.

Reference: Chiapas: Mpio. Ocosingo, 1.5 km al SW de la Colonia Benito Juarez Miramar, sobre el camino a Tierra y Libertad, 25.VIII.1993, A. Reyes & M. Sousa S. 2289 (MO).

15. Digitaria insularis (L.) Mez ex Ekman, Just s Bot. Jahresber. 31(1,5): 778. 1904. Andropogon insularis L., Syst. Nat. (ed. 10) 2: 1304. 1759. Type: Jamaica, no date, P. Browne s.n. (lectotype: LINN-1211.20, designated by Hitchcock, Contr. U. S. Natl. Herb. 12: 126. 1908).

Distribution: U.S.A., Mexico (Ags., Camp., Chih., Chis., Coah., Col., Dgo., Gro., Gto., Hgo., Jal., Mor., Nay., N.L., Oax., Pue., Qro., Q.R., S.L.P., Son., Tab., Tamps., Ver., Yuc.), C. Amer., S. Amer, Car. Native weed.

Reference: Queretaro: Mpio. Jalpan, al ENE de carretera a Tancama, 14.VIII.1985, E. Carranza 1970 (MEXU).

16. Digitaria leucites (Trin.) Henrard, Meded. Rijks-Herb. 61: 6. 1930. Panicum leucites Trin., Gram. Panic. 85. 1826. Based on Milium velutinum DC., Cat. Pl. Horti Monsp. 126. 1813. Type: Mexico, cultivated in Hort. Monsp. from seeds sent in 1804 by Sesse from Mexico, (holotype: MPU-DC; isotypes: US fragm. ex MPU-DC).

Distribution: Mexico (Chis., D.F., Dgo., Hgo., Jal., Mex., Mich., Mor., Oax., Pue., Tab., Tlax., Ver.), C. Amer., S. Amer. Native.

Reference: Michoacan: Mpio. Villa Escalante, Ejido Cuitzitan, potrero Huaniqueo, 8 km SE de Villa Escalante, 24.X.1941, J. Garcia P. 1555 (MEXU).

17. Digitaria leucocoma (Nash) Urb., Symb. Antill. 8: 24. 1920. Syntherisma leucocomum Nash, Bull. Torrey Bot. Club 25(6): 295. 1898. Type: United States of America: Florida, Lake Co., Lake Ella, 3.VII.1894, N. Nash 1155 (holotype: NY; isotype; US).

Distribution: U.S.A., Mexico (Chis.), C. Amer., Car. Native.

Reference: Chiapas: Mpio. Ocosingo, 5 km NE of Ocosingo on road to Palenque, 9.XI.1981, D. E. Breedlove & G. Davidse 55194 (MEXU).

18. Digitaria michoacanensis Sanchez-Ken, sp. nov. Type: Mexico. Michoacan, municipio de Tingambato, Llano de Canaguio, al NE de Pichataro, pastizal secundario, 2600 m, 31.VIII.1989, H. Diaz Barriga & E. Perez 5930 (holotype: IEB).

Distribution: Mexico (Mex., Mich.). Endemic.

Reference: Michoacan: Mpio. Quiroga, Cerro Azul, al N de Quiroga, 23.VII.1980, J. Caballero & C. Mapes 1190 (MEXU).

19. Digitaria milanjiana (Rendle) Stapf, Fl. Trop. Afr. 9: 430. 1919. Panicum milanjianum Rendle, Trans. Linn. Soc. London, Bot. 4: 56. 1894. Type: Malawi: Mount Milanje, October, A. Whyte s.n. (holotype: BM).

Distribution. U.S.A., Mexico (Col., Hgo., Jal., Mor., Pue., Qro., Tab., Tamps., Ver.), O. W. Introduced, pasture.

Reference: Queretaro: Mpio. Jalpan de Serra, Rancho Panelilla, 18.VII.1994, R. Ramirez L. s.n. (MEXU).

20. Digitaria nuda Schumach., Beskr. Guin. Pl. 45. 1827. Type: Ghana, no date, P. Thonning 367 (holotype: C; isotype: L).

Distribution: U.S.A., Mexico (Chis., Col., Gro., Gto., Jal., Mex., Mich., Mor., Nay., Oax., Pue., Q.R., S.L.P., Sin., Ver., Yuc.), C. Amer., S. Amer., Car., O. W. Introduced, pasture.

Reference: Guanajuato: S del poblado de Acambaro, km 15 carretera Acambaro-Zinapecuaro, 3.XI.1992, J. C. Castaneda L. 82 (MEXU).

21. Digitaria obtusa Swallen, Phytologia 4(7): 425. 1953. Type: Guatemala; Alta Verapaz, VIII.1912, H. von Tuerckheim 3793 (holotype: US; isotype: MO).

Distribution: Mexico (Chis., Ver), Guat. Native.

Reference: Chiapas: Mpio. Teopisca, Belem, 8 km NW of Teopisca, along hwy to San Cristobal de las Casas, 15.XI.1984, G. Davidse et al. 29778 (MEXU).

22. Digitaria paniculata Soderstr. ex McVaugh, Fl. Novo-Galiciana, 14: 143-144. 1983. Type: Mexico: Jalisco; 13 mi SSW ofAutlan, 12.VIII.1969, R. L. Wilbur & C. R. Wilbur 2267 (holotype: MICH).

Distribution: Mexico (Jal.). Endemic.

Reference: Jalisco: Entre el crucero La Rosa y Las Marias, 27.VIII.1991, B. R. Benz, F. J. Santana M. & J. Cevallos 1230 (MEXU).

23. Digitaria patens (Swallen) Henrard, Blumea 1(1): 99. 1934. Trichachne patens Swallen, Amer. J. Bot. 19(5): 442. 1932. Type: United States of America: Texas, near Lake Mitchell, San Antonio, 24.VII.1910, A. S. Hitchcock 5328 (holotype: US; isotypes: LL, MO).

Distribution: U.S.A., Mexico (Coah., N.L., Son.). Native.

Reference: Coahuila: 12 mi W of San Buenaventura, 1.X.1966, J. R. Reeder & C. G. Reeder 4573 (US).

24. Digitaria pubiflora (Vasey) Wipff, Sida 19(4): 923. 2001. Panicum autumnale Bosc ex Spreng. var. pubiflorum Vasey, Dept. Agric. Bot. Div. Bull. 8: 35. 1889. Type: United States of America: Texas, El Paso Co., Mts. Near Paso del Norte, 1881, G. R. Vasey s.n. (lectotype: US; isolectotype: US, designated by Wipff & Hatch, Syst. Bot. 19(4): 625. 1994).

Distribution: U.S.A., Mexico (Chih., Coah., Dgo., Gto., Jal., N.L., S.L.P., Son., Tamps., Ver., Zac.). Native.

Reference: Guanajuato: Mpio. Xichu, restos de la mina Zarco, 19.IX.1981, J. Sanchez C. 201 (MEXU).

25. Digitaria sanguinalis (L.) Scoop., Fl. Carniol. (ed. 2) 1: 52. 1771. Panicum sanguinale L., Sp. Pl. 1: 57. 1753. Type: cultivated (LINN-80.31).

Distribution: U.S.A., Mexico (Ags., B.C. Sur., Chih., Jal., Mich., N.L., Qro., S.L.P., Son., Tamps., Zac.), C. Amer., S. Amer., Car., O. W. Introduced, weed.

Reference: Michoacan: Tuxpan de Michoacan, 1.IX.1981, A. Diaz, A. Vargas & A. Mendez 273 (MEXU).

26. Digitaria sellowii (Mull. Hal.) Henrard, Blumea 1: 99. 1934. Trichachne sellowii Mull. Hal., Bot. Zeitung (Berlin) 19(43: 315. 1861. Type: Brazil: Brasilia, no date, Sellow s.n. (holotype: B).

Distribution: Mexico (Chis., Hgo., N.L., Oax., Pue., Qro., S.L.P., Tamps., Ver., Yuc.), C. Amer., S. Amer., Car. Native.

Reference: Veracruz: about 1 mi N of Omealco, 15.XII.1972, J. R. Reeder & C. G. Reeder 6020 (MO).

27. Digitaria setigera Roth, in Roem. & Schult. Syst. Veg. 2: 474. 1817. Type: India, no date, B. Heyne s.n. (holotype: B; isotypes; B, K).

Distribution: U.S.A., Mexico (Camp., Chis., Oax., Ver.), C. Amer., S. Amer., Car., O. W. Introduced, pasture.

Reference: Chiapas: ejido Las Golondrinas lower slopes of Cerro Ovando, along road between Golondrinas and Los Cacaos, 22.VIII.1996, T. B. Croat 78528 (MO).

28. Digitaria ternata (A. Rich.) Stapf, Fl. Cap. 7: 376-377. 1898. Cynodon ternatus A. Rich., Tent. Fl. Abyss. 2: 405. 1851. Type: Ethiopia: Tigray, prope Adoua, no date, no collector (lectotype: P; isolectotypes: B, K, L, US, WAG, designated by Hernard, Monogr. Digitaria 738, 1950).

Distribution: Mexico (Ags., D. F., Dgo., Gto., Hgo., Jal., Mex., Mich., Mor., Oax., Pue., Qro., Zac.), S. Amer., O. W., Introduced, weed.

Reference: Michoacan: 5 km al S of La Piedad, 6.XII.1980, A. A. Beetle, G. Hardin & R. Guzman M. 6321 (MEXU).

29. Digitaria texana Hitchc., Proc. Biol. Soc. Wash. 41: 162. 1928. Type: United States of America: Texas, Sarita, 27.VI.1910, A.S. Hitchcock 5479 (holotype: US).

Distribution: U.S.A., Mexico (Ver.). Native.

Reference: Veracruz: Veracruz, 31.VIII.1910, A. S. Hitchcock 6554 (US).

30. Digitaria velutina (Forssk.) P. Beauv., Ess. Agrostogr. 51, 173. 1812. Phalaris velutina Forssk., Fl. Aegypt.-Arab. 17. 1775. Type: Yemen, no date, Forsskal 115 (holotype: C).

Distribution: Mexico (D.F., Mor., Oax., Pue.), C. Amer. O. W. Introduced, weed.

Reference: Distrito Federal: Campus of Universidad Nacional Autonoma de Mexico, 1.XII.2011, J. G. Sanchez-Ken s.n. (MEXU).

31. Digitaria violascens Link, Hort. Berol. 1: 229. 1827. Type: Brazil; Brasilia, no date, Anon. s.n. (holotype: B; isotype; BAA fragm. ex B).

Distribution: U.S.A., Mexico (Chis., Ver.), C. Amer., S. Amer., Car. Native.

Reference: Veracruz: carretera Xalapa-Coatepec por Briones, vivero anexo a Asuntos Ecologicos, frente al Jardin Botanico, 24.VI.1997, M. J. Lizama 697 (MEXU).

ACKNOWLEDGMENTS

Many thanks to M. B. Mendoza G. for the scanning electron microscope (SEM) images.

LITERATURE CITED

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Henrard, J. 1950. Monograph of the genus Digitaria. Universitaire Pers Leiden. Leiden, The Netherlands. 999 pp.

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Pohl., R. W. and G. Davidse. 1998. Digitaria. Haller, Nom. Cons. In: Davidse, G., M. Sousa S. and A. O. Chater (eds.). Flora Mesoamericana, Vol. 6. Alismataceae a Cyperaceae. Universidad Nacional Autonoma de Mexico. Mexico, D.F., Mexico. pp. 365-371.

Rugolo de Agrasar, Z. E. 1974. Las especies del genero Digitaria (Gramineae) de la Argentina. Darwiniana 19(1): 65-166.

Sanchez-Ken, J. G. 2010. Two new species of Paspalum (Paniceae: Panicoideae: Poaceae), a preliminary checklist of the genus in Mexico, and the identity of P. crinitum. Rev. Mex. Biodiv. 81: 629-647.

Sanchez-Ken, J. G. 2011. Two new species of Urochloa (Paniceae; Panicoideae; Poaceae) from Western Mexico and the updated checklist with a key to species of the genus in Mexico. Syst. Bot. 36(3): 621-630.

Soreng, R. J., G. Davidse, P. M. Peterson, F. O. Zuloaga, E. J. Judziewicz, T. S. Filgueiras and O. Morrone. 2003 and onwards. Catalogue of New World grasses. Available from: www.tropicos.org/Project/CNWG (accessed November 2011).

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Swallen, J. R. 1953. New grasses from Guatemala. Phytologia 4(7): 423-427.

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Recibido en septiembre de 2011.

Aceptado en julio de 2012.

J. GABRIEL SANCHEZ-KEN

Universidad Nacional Autonoma de Mexico, Instituto de Biologia, Departamento de Botanica, 04510 Mexico, D.F., Mexico.

sanchezken@ibiologia.unam.mx
Table 1. Differences between Digitaria michoacanensis and D. badia.

Character               D. michoacanensis       D. badia

Height (cm)                15-30(-55)             60-80
Internode length              short             elongated
Node indumentum           puberulent to     short hirsute to
                           scabrellous          glabrous
Sheath margin             short pilose      short hirsute to
  indumentum                                    glabrous
Ligule length (mm)           0.3-0.6             0.5-1.3
Blade length (cm)         3.2-5.7(-10)          (4-)7-20
Blade abaxial               glabrous        papillose-hirsute
  indumentum                                     toward
                                                  apex
Raceme number                 2(-3)            (2-)3-4(-5)
Peduncle indumentum         glabrous        sparsely to dense
                                               long-pilose
                                             toward the apex
Spikelet length (mm)         2.6-2.7             2.3-2.6
Spikelet width (mm)          1.3-1.4              1-1.1
Spikelet hair tips         truncate to          apiculate
                             rounded
1st glume length (mm)        0.3-0.5            up to 0.2
1st glume indumentum         pilose             glabrous
2nd glume length (mm)         2-2.7              1.9-2.2
Sterile lemma vein              5                   7
  number
Fertile lemma length         2.6-2.7             2.2-2.4
  (mm)
Fertile lemma width           1-1.1              0.7-0.9
  (mm)
Anther length (mm)           1.3-1.4              1-1.1
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