POA MATRI-OCCIDENTALIS (POACEAE: POOIDEAE: POEAE: POINAE), A NEW SPECIES FROM MEXICO

2006·7 MB·English

by  Paul M Peterson

POA
MATRl-OCCIDENTALIS POOIDEAE
(POACEAE:
NEW
A FROM
MEXICO
POEAE:
POINAE), SPECIES
and
Paul M. Peterson Robert Soreng Yolanda Herrera
Arrieta
J.
Department of Botany COFAA
CIIDIR-Dgo.,
Museum
National of Natural History Instituto Politecnico Nacional
Smithsonian Sigma 20 de Noviembre
Institution Fracc.
s.n.
II
DC
Washington^ 2001 3-701 USA. 34220 Durango^ Durongo, MEXICO
2^
[email protected]; [email protected] [email protected]
ABSTRACT
&
Poa matri-occidentalis PM, Peterson Soreng, sp nov., described and illustrated. Poa matri-occidintalis subsp.
is
known
maln-occidenialis from steep rocky slopes of Cerro Gordo, Durango, and Poa main-occideutaUs subsp.
is
&
known
mohinoreitsis Soreng P.M. Peterson, subsp. nov, is from rocky cliffs of Cerro Mohmora, Chibuabua. Tbe
new
species morpbologically similar to Poa kelloggii but differs by baving leaf sbeatbs tbat are closed near the
is
mm
base 2/3 to 4/5 their length, entire ligules that are 3.5-6 long, noddnig panicles, ovate lemmas with obtuse
to
acute apices, and non-visible rachilla internodes. A key distinguishing species now reported from northern
11
Mexico
provided.
is
RESUN4EN
&
Se describe e ilustra Poa matri-occidentalis P.M. Peterson Soreng, sp, nov. Poo nuftri-occidcntalis subsp. mfliri-
iKcidenialis se encuentra en la zona de cuestas rocosas escarpadas de Cerro Gordo, Durango. y Poa matri-occideutalis
&
subsp. mohinoreiisis Soreng PM. Peterson, subsp. nov. se encuentra en la zona de laderas rocosos del Cerro
Mohinora, Chihuahua. La nueva especie es morfologicamente similar a Poa kelloggii pcro difiere de csta ultima
por tener las vainas de las hojas cerradas en la parte inferior de la base de 2/3 a 4/5 dc su longitud, por tener
mm
ligukis enteras de 3.5-6 de largo, paniculas recurvadas, lemas ovadas con apices agudos a obtusos y raquilla
con entrenudos no-visibles. Se proporciona una clave para distmguir las 11 especies reportadas actualmente del
norte de Mexico.
m
Poa L. is the largest genus of grasses, including some 500-575 species that occur a wide
range of habitats from throughout the World (Soreng 1990; Gillespie &r Soreng 2005).
The genus characterized by having rather small, multi-flowered spikelets, lemmas that
is
commonly
are keeled, unawned, usually S-nerved, with web-like hairs emerging from
the dorsal side of the callus, caryopses that are firm with lipid and a short hilum, lodi-
cules that are broadly lanceolate with a lateral lobe, leaf sheaths closed above the base
more than 1/20 the entire length, leaf blades that generally have two rows of buUiform
cells (one on either side of the midnerve, these appearing as railroad tracks) and no addi-
rows and commonly
tional of bulliform blades with naviculate (boat-shaped) api-
cells,
m
ces (Soreng, press). Poa has been divided into subgenera and sections and subsections
New
for North America (Soreng 1998; Soreng in press), the World (Soreng et 2003aX
al.
and World Zhu
the (Gillespie et 2006; et 2006).
al. al.
Northern Mexico (excluding Baja California and Baja California Sur) not thought
is
to be especially rich in Poa species. The following species have been reported from the
11
states of Aguascalientes (Ags), Chihuahua (Chih), Coahuila (Coah), Durango (Dur) Jalisco
Nuevo Leon (NL), San Luis Potosi (SLP), Sonora (Son), Tamaulipas (Tamp), and
(Jal),
Zacatecas (Zac): Poa annua L. (Ags, Chih, Coah, Dur, NL, SLP, Tamp, Zac), P bigelovii
Jal,
&
Vasey Scribn. (Chih, Coah, NL, Son), compressa (Coah), P conghmeraia Rupr. (= P
L.
P.
scaherula Hook, [Coah an error since a specimen A, Garcia cited in Beetle
is "^9) et
f.) al.
(J
SIOA22(2);905-914.2006
906 BRIT.ORG/5IDA
22(2)
P
(1999) = pratcnsis Pjendleriana (Stcud.) Vasey [includes PJcndleriana subsp.
is L.],
albescens (Hitchc.) Soreng] (Chili, Coah, Son, Zac), P nfirma Kunth (listed as synonym of
i
P annua and probably with similar distribution), P mulleri Swallcn (NL), P orizahcnsis
&
Hitchc. (NL possibly an error for CH. MJ. Mueller 1248 from Cerro Potosi as deter-
mined P
by A. A. Beetle - mullcril SLP-not yet verified by us from there), P prate n sis (Chi\
Coah, NL), P ruprechtii Peyr. [includes Rsharpii Swallenasa synonym] (Coah,NL,), and
P
strictiramea Hitchc. (Chih, Coah, Dur, NL, Zac) [Beetle et al. 1999; Espejo Serna et al.
known
2000; Hitchcock Of the 10 species from the region, P,annua,Rcompressa,P.
1913].
and and P
injirma, pratcnsis are introduced, higclovii, PJcndleriana, mulleri,
P. P. P.
orizahcnsis, P ruprechtii, and P strictiramea are native. The annuals, P annua and P
injirma have been placed in Poa sect. Micranthcrac Stapf, and P bigclovii was placed in
m
Poa sect. HomaJopoa Dumort. (Soreng et al. 2003a). 01 the remaining natives, P ullcri,
P.
orizahcnsis, ruprechtii, and PsLriciiramea have been placed Poa Uomalopoasl,
in sect.
P.
and was Madropoa
PJcndleriana placed in Poa Soreng (Soreng 2003a).
sect. et
al.
While making
determinations of material in the field using Las Gramineas de
Durango (Herrera Arrieta 2001) and then checking the herbarium Centro
at
m
Interdiciplmario de Investigacion para Desarrollo Integral Regional (CIIDIR)
el
Durango, the first author recognized the unique features of a recent collection from Cerro
Upon
Gordo. further inspection of collections on loan from various herbaria com-
for a
plete revision of Poa in Mexico, the second author discovered another, generally pubes-
cent form, occurred near Cerro Mohinora, Chihuahua. The third author then contrib-
We
uted the anatomical portion. describe these two new forms as a new species of Poa
new
with two subspecies. The species with two subspecies clearly aligned within sub-
is
family Pooicleae, tribe Poaeae, and subtribe Poinae (Soreng 2003a, 2003b, 2005).
et
al.
&
Poa nov
matri-occidentalis P.M. Peterson Soreng, sp. (Figs, la-c; 2c-l). MFiXICO.
Tvpi-;
SW
DuRANCO: Sierra Madre Occidental, slope of Cerro Gordo just below twin rock outcrops (23°12'32.5"N-
&
104°56'541"W), 3130-3200 m, 26 Sep 2005, P.M. Peter sou 19M5 Sanchez Alvarado (woLorwr.:
US!;
F.
ISOTYPFS CIIDIR!; MIZXU!).
mm
A
Poa helloggii Vasey vaginibus connarus 2/3-4/5 longe lateque, ligulis 3.5-6 longis inregris. paniculus nutans,
lemaribus ovaris apicibus obrusus ad acurus, rachiUibus no
visibilis, recedit.
Loosely caespitose and rhizomatous perennials with intra and extravaginal basal branch-
cm
Culms 45-80
decumbent,
ing. solitary to several, erect or bases slightly terete or
tall,
weakly compressed; nodes 2-4, terete, glabrous and smooth, 1-3 exserted. Leaf sheaths
cm
mostly 3~14
long, closed about 2/3 to 4/5 their length, compressed, glabrous and
smooth, or sometnnes the lower ones retrorsely scabrous puberulent and w4th cihate
to
most sheaths 0.4-Ll tunes long smooth with few
collars, as as their blades; collars or a
mm
membranous
hooks, glabrous or ciliate; ligules 3.5-6 long, to hyaline, glabrous and
mm
smooth, or sometimes puberulent, apex obtuse to acute, entire; blades 2-6 wide,
flat,
abaxial nerves and margins lightly scabrous, adaxially smooth, glabrous throughout,
cm cm
apices narrowly prow-shaped; flag blades 12-22 long. Panicles 12-26 long, nod-
cm
24-85
ding, pyramidal, open, sparse with spikelets, longest intcrnodes 2.5-5.5 long;
cm
branches (l-)2(-3) the lower nodes, longest 5.5-10 long bearing 3-15
at spikelets, as-
mm
cending 4-8
to spreading, lax, angled, the angles sparingly scaberulous. Spikelets
mm
long, 1.8-2.7 wide, laterally compressed, greenish to stramineous, florets 2 or per-
3,
much
fect, occasionally the upper floret reduced and lower rachilla intcrnodes
is sterile;
mm
1-2 long, usually not visible, glabrous, smooth; glumes equal to subequal, lanceolate,
PETERSON ET AL, POA MATRI-OCCIDENTALIS, A NEW SPECIES FROM MEXICO
907
&
hQA.Poamatri-occidentalissubsp.matri-occidentalis [Peterson T 91 45 Sanchez Alvarado).^. Habit. B. Inflorescence.C.Sheath, ligule,
and blade, Poa matri'occidentalis subsp. mohinorensis (Nesom 6475 & McDonald), D. Sheath, Iigule,and blade.
BRIT.ORG/SIDA 22(2)
908
L
2,Poa matri-occidentdis subsp. mohinorensis {Nesom 6475 & McDonald], Spikelet. B. Floret. Poa matri-occidentafis subsp.motrh
Fig.
Lemma.
19145 & 5dnchezAlvarado).C Lower glume, Upper glume. G. H. Palea, dorsal
occidentalis {Peterson Spikelet. D. Floret. E. F.
view. Palea, ventral view. J. Stamens, ovary, and lodicules enclosed in palea. K. lodicules. L.Young caryopsis.
I.
PETERSON ET AL.,POA MATRI-OCCIDENTALIS,A NEW SPECIES FROM MEXICO
909
scabrous along upper
the
keel, distinctly keeled, 3-nerved, the lateral nerves often only
evident near base, scaberulous along the nerves, apex acute acuminate,
to often appear-
mucronate
ing because margins
the are often involute, margins hyaline; glumes
lovv^er 3
mm
mm
5 long, lanceolate to ovate usually shorter than the upper; upper glumes
3.7-5.6
long, ovate to obovate, wider that the lower with more prominent with
nerves; calluses
cob-webby
hairs, the hairs about 1/2 to 1/3 the length of the lemma; lowest lemmas 4.6-
mm
6.3 long, ovate, distinctly keeled, surfaces between nerves finely muriculate (with
minutely bumps
pointed, whitish on the short cells) or sometimes densely scabrous, 5-
nerved, the lateral nerves moderately prominent, keel and nerves
lateral scabrous, keel
and
marginal nerves glabrous or sometimes puberulent below, margins hyaline, apex
mm
obtuse to acute; lowest paleas 4.4-6 long, usually a shorter than the lemmas,
little
strongly laterally compressed with deep adaxial furrow between
a the nerves, muriculate,
mm
scabrous along
the nerves; anthers 2-2.2 long, yellow; lodicules membranous; ovary
2,
mm
Caryopses
glabrous. 2.6~2.9 long, fusiform, light brownish.
Phenology— Flowering August through
October.
Comments.
ogg^
2/3 4/5
to
mm
nodding lemmas
long, panicles, ovate with obtuse acute and
to apices, non-visible
rachilla internodes.
Poa
matri-occidentalissubsp
matri-occidentalis
(Figs, la-c; 2c-l; 3a-c;
4).
Lower
leaf sheaths glabrous and smooth; smooth with few
collars or a hooks, glabrous;
mm
ligules glabrous and smooth. Lowest lemmas 4.7-5.4 long, surfaces between nerves
finely muriculate (with minutely pointed, whitish-bumps on and
the short
keel
cells),
marginal nerves scabrous, glabrous throughout.
—Known
and
Distrihution habitat only from
a single locality Cerro Gordo,
at
m
Durango, between 3130-3200 where
the species was found growing on rocky
steep,
and
grassy slopes beneath open Pseudotsuga
forests of me?T^iesii (Mirb.) Franco, Qucrcus
sp., Finns spp., with other associates, such Arctostaphylos pungcns Kunth, Bromus
as:
&
&
carinatus Arm, Humb.
tiook. richardsonii Link, Acgopogon
B. ccnchroidcs Bonpl. ex
Willd., Trisetum ride (Kunth) Kunth, Festuca Carex and
vi Agrostis
sp., sp., sp.
anatomy—
Lea/ Cross-sections were done by hand on
re-hydrated material then
mounted on temporary and A
with
slides stained concentrated safranm. diagram
of a
and made
cross-section abaxial leaf scrape were with the aid of a camera lucida (Figs.
3a-c,
4).
view
Cross-section (Fig. 3a-c.).-The lamina are V-shaped with primary secondary
and
tertiary vascular bundles of decreasing The primary vascular bundles
size. are well
xylem
differentiated into with metaxylem, phloem, and double bundle sheath (mestome
a
and parenchyma
bundle The rounded and
sheath). ribs are furrows are <l/5 as deep as
the width of the blade adaxially and abaxially Abaxial projection of the midrib caused
by parenchyma
inflated and sclerenchyma
cells is conspicuous. In half-the-width of the
blade there is a single primary vascular bundle comprising the midvein; 3-4 additional
primary 3-4
vascular bundles; secondary vascular bundles placed between consecutive
tertiary vascular bundles; 7-8 tertiary vascular bundles placed between each consecu-
tive primary and secondary vascular bundles; and two vascular bundles
tertiary at the
m
margin
(Hii-ii-iii-i-iii-ii-iii-i-iii-ii-iii-i-iii-ii-iii-iii). All vascular bundles are placed the
median
layer of the blade and are round in outline. The xylem of the primary vascular
BRIT.ORG/5IDA
22(2)
910
C
A
B
anatomy 19145 &SdnchezAlvaraclo),a(idim\
FiG^.Cross-section leaf blade of Podm£?fn-Ofc/rfe;)ffl//5Subsp.mflrn-ofdrf^^
=
surface uppermost in all drawings. A. Primary vascular bundle. B. Secondary vascular bundle. C. Tertiary vascular bundle. Scale bar
50um.
&
Abaxial leaf epidermis of Poa matri-occidentalis subsp. matri-occidentalis {Peterson 19145 Sanchez Alvarado) showing long
Fig. 4.
=
cells, silica bodies (dark), cork cells (clear), and three stomata. Scale bar 50um.
bundles contains two or occasionally three metaxylein vessels adjacent to the phloem,
that are larger than the parenchyma bundle sheath cells, and sometimes one or two pro-
toxylem vessels are located adaxially to the phloem. The mestome, or inner sheath, is
always present in primary and secondary vascular bundles surroundmg the xylem and
phloem. The Mestome composed small with thick walls and mterrupted
of cells
is
abaxially by sclerenchyma fibers forming a girder in primary and secondary bundles,
surroundmg
except in the central primary vascular bundle where continuous the
it is
bundle and the sclerenchyma separated from the bundle by colorless cells and cen-
is
tered at the very bottom of a conic abaxial base. The parenchyma bundle sheath, or outer
layer, contains large, thin-walled cells; 10-12 cells are present on the continuous adaxial
half cncle of the primary vascular bundle sheath; 6-8 cells are present in the secondary
vascular bundles; and the number of cells varies between three and four on each side of
Chlorenchyma surround bundles and
the interrupted tertiary vascular bundles. cells the
arc conspicuously continuous between the vascular bundles in a loose arrangement. Five
PETERSON AND SORENG, POA MATRI-OCCIDENTALIS, A NEW SPECIES FROM MEXICO
911
sclerenchyma
eight
to fibers are present adaxially in all bundles. Five to eight rows of
sclerenchyma form
fibers the abaxial girders of the primary and secondary vascular
bundles, vv^hich vv^iden near the epidermis and narrov^ tovv^ard the vascular bundle. Deep
fan-shaped
rou^s of bulliform cell are located adaxially near the central part of the blade
betv/een the central primary vascular bundle and two
lateral tertiary vascular bundles;
these are continuous to adaxial epidermal walls.
cell
Epidermis abaxial view and
in (Fig. 4).-Costal mtercostals zones
are clearly distin-
Three rows
guishable. to six of short cells are found in the costal zone, each separated by
row
long
a of Irregularly-shaped bodies and
cells. silica are alternate adjacent short
to
cells of the costal zone. Cork cells are less frequent and the same shape as the bod-
silica
common
ies. Fifteen to seventeen rows of long cells are in the intercostal zone. Long
cells
are 8-10 times longer than wide with wavy No
cell walls. papillae or hairs are present.
Low
dome-shaped
stomata and
are infrequent found
in single row. Parallel subsidiary
m
A
rounded
cells are outline. few antrorse bristles are present margin.
at foliar
&
Poa
matri-occidentalis subsp. mohinorensis Soreng nov
P.M. Peterson, subsp. (Figs. Id;
2a, Type MEXICO. N
b). Ci iii iuahua: Municipio de Guadalupe y Calvo, Sierra Madre Occidental, side of
SW
Cerro Mohinora, ca. 13 mi of Guadalupe y Calvo, open pine-fir woods with scattered spruce, neady
many
vertical, N-facing rocl< wall, very moist with bryophytes and rich herbaceous flora (25''57'N-
&
Aug
107°03'W), 2950 m, 20 1988, G. Nesom 6^75 A. McDonald (holotyph: TEX!; ISOTYPH ARIZ).
A
Poa matri-occidentalis subsp. matri-occidentalis vaginae disatalibus lemmatae carina puberulens,
et
internervibus
scabris, differt.
Lower
leaf sheaths retrorsely scabrous puberulent;
to collars ciliate; ligules puberulent.
mm
lemmas
Lov^^est 4.6-6.3 long, surfaces betvv^een the nerves densely scabrous, keel and
marginal nerves scabrous and puberulent
below.
Known
Distribution and habitat— only from Cerro Mohinora, Chihuahua between
2950-3130 m, on moist, rocky cliffs and ledges associated with open A
forests of Pi n
us, hi es,
and
Picea.
Additional specimen examined. MEXICO. Chihuahua: Mumcipio de Guadalupe y Calvo, Sierra Madre Occiden-
tal on bigh ledges on summit of Cerro Mohinora (25"57'N-1 07^03'W), 10,000-10,300 16-17 Oct Corrdl
1959, D.5.
it,
&HS.
23177 Gentry
(LL).
DISCUSSION
Based on morphological similarity Poa endemic
to hcUoggii, to California, matri-
P.
m
occidentalis tentatively placed Poa Syhestres YL. Marsh ex Poa
is sect. Soreng,
sect.
Sylvestres as treated for the genus in the Flora of North America, includes seven
species,
all of v^hich are endemic to forests in the U.S.A, and southern Canada (Soreng
in
press).
[Poa Sylvestres slightly modified from Soreng
sect. in press] "Plants perennial; usu-
non-rhizomatous and
ally sometimes
non-stoloniferous, shortly rhizomatous, usually
loosely tufted, infrequently densely tufted. Basal branching mainly pseudointravaginal,
sometimes mainly Culms
20-126
or extravaginal. cm, weakly
terete or compressed.
Sheaths
closed about weakly
(1/20)1/3 to their full length, terete or keeled, basal sheaths
mm
readily deteriorating; ligules 0.1-3(-4) long, smooth or sparsely scabrous, truncate
smooth
to obtuse, entire or lacerate, or blades smooth
ciliolate; or scabrous, glabrous, api-
cm
ces narrowly prow-shaped. Panicles 4-36 pyramidal
long, erect or lax, or lanceoloid,
usually
sparse, lovs/er rachis internodes usually longer than (2-)3 cm, nodes with 1-10
branches; branches ascending
spreading
to or eventually ref lexed, lax or straight, angled,
mm
angles scabrous, spikelets confined to distal l/5-l/3(-l/2). Spikelets 2.5-8.2 long,
BRIT.ORG/SIDA 22(2)
912
normal; rachiUa internodcs smooth, usually gla-
laterally compressed; florets (l-)2-5(-6).
mm
Glumes on
brous, sometimes hairy, hairs to 0.2 long. distinctly keeled, scabrous the
webbed,
and compressed, usually dorsally
keel nerves; calluses terete or slightly laterally
mm
sometimes glabrous; lemmas 2.1-5 long, lanceolate to broadly lanceolate, distinctly
keeled, glabrous or hairy, apices with narrow, clear or white margins; palea keels sca-
mm
15
brous, gkibrous or with hairs over the keels; anthers 0.4-2(-2.6) long.
3,
DNA
Based on sequence analyses, Poa Sylvcstrcs the earliest diverging section
sect. is
we now
in the genus, Arctopoa (Griseb.) Prob. is excluded, as believe it should be
if
m
new some from
However, the species differs in respects all or
(Gillespie et prep.).
al.
R
most of the other species in the section. Like hellog^^ii, matri-occidentaUs is short
P.
rhizomatous and basal branching primarily extravaginal. Poa matri-occidcntalis
its is
mm
from the other species in the section by having longer ligules (3.5-6 long).
differs all
DNA
new confirmed belong section sequence analysis)
the species to to this (viz. it
If is
would be the report from outside the U.S.A. and Canada. Our only hesitation to plac-
first
new some morphological overlap with Poa
ing the species in this section is that there is
Homalopoa and with the R nervosa (Steud.) Vasey complex of Poa sect. Madropoa,
sect.
s.l.
DNA
and currently, there are no data for the new species. In Poa sect. Madropoa, through
most approaches P Vasey from
mohinorensis, matri-occidenialis closely tracyi
subsp.
P.
New and Rccder
Mexico and Colorado noted on the 1989 annotation by C.G.
U.S.A. (as
J.R.
name from
on Ncsom 6475), and "P ruprcchtii Peyr." (as that is applied to material the
from both by
MadreOrientak Mexico). mdtri-acciden differs these species
Sierra Poc? talis
new
on lemmas and only The
having muriculate or short-pubescence the perfect flowers.
species differs from T. ruprcchtir by having longer glumes that are also proportionally
We
lemmas and by fewer per suspect the
longer relative to the adjacent florets spikelet.
m
name P may be misapplied northern Mexicos Sierra Madrc Ori-
ruprcchtii
Pcyr.
str.
s.
by Hitchcock and Fournicr from the region of
ental as material called this (1913) (1886),
m
the type locality in the State of Mexico and Distnto Federal, differs having short an-
lemmas
and more indurate and prominently nerved with relatively longer glumes,
thers,
but we have yet to locate and examine a type specimen of P ruprcchtii. If our suspicion is
new
correct, the Sierra Madre Oriental plants probably represent an additional species.
A key known or reported species from northern Mexico follows. In this key
to all
measurements were taken from the lowest, one or two florets in the best-developed
all
spikelets.
KEY TO THE OF POA NORTHERN MEXICO
SPECIES
IN
pubescent
Plants annual; palea keels part.
in
1
.
with cobwebby panicles contracted bigelovii
Callus hairs; P.
2.
Callus glabrous; panicles open.
2.
mm
_P.annua
Anthers 0.6-1 long
3,
mm
infirma
Anthers 0,2-0.5 long P.
3,
Plants perennial; palea keels scabrous only,
1.
fum webbed.
Anthers 0.5-1 long callus
4.
Lemmas glabrous or very sparsely puberulent on the keel base; spikelets broadly ovate
5,
P.orizabensis
Lemmas short villous on the keel and lateral nerves and som^etimes puberulent between
5.
the nerves; spikelets broadly lanceolate (of Distrito Federal and State of Mexico) P. ruprechtii
mm
Anthers 1,2-3 long; callus glabrous or pubescent.
4.
Plants without rhizomes or lateral tending shoots,densely tufted, vegetative shoots mainly
6,
intravaginal.
PETERSON AND SORENG, POA MATRI-OCCIDENTALIS, A NEW SPECIES FROM MEXICO 913
Upper glumes (3-)5-7-nerved; lemmas pubescent on lower half of the keel; longest
7.
cm cm
branches up to 3.5-3.8 long; plants 20-42 mulleri
tall P.
Upper glumes 3-nerved; lemmas glabrous or very sparsely puberulenton the keel and
7.
cm
marginal nerves near the base; longest branches up to 10 long; plants mostly (20-)
cm
40-100
strictiramea
ta
P.
Plants with rhizomes or lateral tending extra vaginal shoots, densely to loosely tufted, veg-
6.
etative shoots intravaginal and extravaginal or mostly extravaginal.
Paniclescontracted,fairlydense;uppermostleaf blades highly reduced or absent; popu-
8,
lations dioecious or pistillate; callus glabrous.
Lemmas
glabrous P.fendleriana sspalbescens
9.
Lemmas
pubescent on the and marginal nerves P.fendleriana ssp.fendleriana
keel
9.
Panicles loosely contracted to wide open; uppermost leaf blades well-developed; plants
8.
all perfectflowered, or, if pistillate in part, then panicles open; callus, at least of proximal
cobwebby
Iemmas,with
hairs or glabrous.
Lemmas
10. glabrous or sparingly puberulent near the base of the keel; upper glumes
mm mm
3.7-5.6 long; ligules obtuse to acute, 3-6 long.
Sheaths of lower leaves retrorsely scabrous to puberulent; collars ciliate; lem
1 1.
mas densely scabrous between the nerves, keels and marginal nerves nerves
puberulent below matri-occidentalis mohinorensis
ssp.
P.
11. Sheaths of lower leaves smooth, glabrous.collars smooth or with a few hooks,
lemmas between and
glabrous; finely muriculate the nerves, keel marginal
nerves glabrous below matri-occidentalis ssp matri-occidentalis
P.
Lemmas
distinctly pubescent on the keel and marginal nerves; ligules truncate to
0.
mm
1-3
obtuse, long.
Culms and nodes strongly compressed, keeled compressa
12. P.
Culnis and nodes terete, or culms weakly compressed.
2.
1
mm
Rachilla internodes mostly hidden from view; spikelets mostly 3-6
13.
long; lemmas glabrous between the keel and marginal nerves; ligules trun-
mm
cate, entire, usually 1-2 long pratensis
P.
mm
Rachilla internodes exposed; spikelets 4.5-8 long;lemma surfaces (at
3.
the proximal most ones) with between the and marginal
least hairs keel
mm
nerves nearthe base;ligules obtuse, irregularly dentate, to 3 long (of
Madre
Sierra Oriental) "P. ruprechtii"
ACKNOWLEDGMENTS
We
wish thank Smithsonian Endowment Fund and
to the Institutions Restricted the
Museum
and Program
Biodiversity, Surveys, Inventories the National of Natural His-
at
tory for supporting the fieldwork. Appreciation extended to Alice R. Tangerini for pro-
is
Gomez
viding the illustrations; Patricia Bustamante for correcting the Spanish resumen,
Dan
Nicolson for correcting the Latin diagnoses; and Jesus Valdes-Reyna and Adolfo
Espejo-Serna reviewing the manuscript.
for
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