keys to the vascular plants of east texas - Botanical Research ...

ARISTIDA/POACEAE
831
BRIT), Newton (Carr 18418, BRIT), and Tyler (MacRoberts et al. 2002a) cos. in the s part of the
Pineywoods; se U.S. from VA s to FL w to e TX. [A. affinis of authors, not (Schultes) Kunth] While
not officially designated as such (e.g., TOES 1993; Carr 2002d; Poole et al. 2002), given its limited
distribution in the state, we consider this species to be of conservation concern in TX. �
Aristida purpurascens Poir., (purplish or turning purple), ARROW-FEATHER THREEAWN, BROOM-
SEDGE, ARROW GRASS. Tufted perennial from a knotty, thickened base, buds and short curvingerect
rhizomes usually present; culms to 2(–4) mm in diam., to 1 m tall; basal leaves persistent
after drying, often curly; panicles narrow, contracted; lemma 5–8 mm long, purple or mottled
with purple at maturity, with central awn 15–30 mm long, more spreading than the lateral
awns; lateral awns 2–10 mm shorter than central. Similar to A. longespica except A.
purpurascens is perennial. The county distribution map does not distinguish varieties. The following
key is adapted from Allred (1986).
1. Central and lateral lemma awns spreading, straight or slightly contorted but not reflexed, all
about the same thickness at the base; glumes usually of different lengths, the lower usually
longer than the upper, 6–10 mm long, the upper glume 5–8 mm long __________________ var. purpurascens
1. Central lemma awn divaricate (= very widely spreading) to reflexed, about twice as thick at the
base as the erect lateral awns; glumes ± equal or the lower slightly longer, both 6–7 mm long ___ var. virgata
var. purpurascens. Woods openings, borders, and prairies, usually on sandy soils; Pineywoods
and Gulf Prairies and Marshes w to Blackland Prairie, also e Edwards Plateau; se Canada (Ont.)
and e U.S. from NY to FL w to NE and TX. Aug–Nov.
var. virgata (Trin.) Allred, (wand-like). Sandy prairies, openings in sandy pinelands, bogs, or
waste places, generally in moist or wet areas; Angelina (Brown 9410, BRIT), Hardin, and Jasper
(SBSC) cos. in the Pineywoods; a Titus Co. collection (Smith 710, BRIT) may be var. virgata but is
ambiguous; also Gulf Prairies and Marshes; e U.S. from NJ s to FL w to TX. This taxon has sometimes
been recognized as a distinct species (e.g., Correll & Johnston 1970; Hatch et al. 1990),
while some authorities (e.g., Gould 1975b; Hatch 2002) submerged it into an undivided A.
purpurascens. Allred (1984a) indicated that when compared with A. purpurascens, there is significant
morphological intergradation and only one species is involved. He later (1986) recognized
A. virgata as a variety. However, the two varieties intergrade (Allred 2003d) and are difficult
to distinguish. Allred (1984a), for example, indicated that sometimes an individual of A.
purpurascens may have spikelets corresponding to more than one variety. While we are following
Allred (1984a, 1986, 2003d) and Kartesz (1999) in recognizing var. virgata, it is possible that
this variety does not deserve formal recognition.
Aristida purpurea Nutt., (purple), PURPLE THREEAWN. Perennial; panicles open or contracted. A
highly variable species, with a number of the varieties having been treated as separate species
in the past. Turner et al. (2003) recognized two species in this complex (A. purpurea including
var. longiseta and A. glauca [our var. nealleyi] including var. wrightii). Because of extensive intergradation,
we are following most recent authors (e.g., Holmgren & Holmgren 1977; Allred
1984b, 2003d; Sutherland 1986; Kartesz 1994, 1999; Hatch 2002) in treating the taxa as varieties
of A. purpurea. Most plants may be separated by the characters given in the key to species and
varieties. This is the most widespread and probably the most abundant Aristida species in TX.
The county distribution map does not distinguish varieties.
var. longiseta (Steud.) Vasey, (long-bristled), RED THREEAWN, DOGTOWN GRASS, LONG-AWNED
ARISTIDA, LONG-AWNED THREEAWN. Panicles contracted or open; glumes unequal, the first 0.5–
0.6 the length of the second, the second 14–25 mm long; lemma 12–16 mm long, 0.3–0.8 mm
wide at apex; lemma awns about equal, very long, 4–10 cm long, rarely longer. Disturbed sites;
mainly Blackland Prairie s and w through w 3/4 of TX; sw Canada and w 1/2 of U.S. e to MN
and LA. Mar–Dec. [A. longiseta Steud., A. reverchonii Vasey] This is the most variable variety of