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

866 POACEAE/CHLORIS
divergent; spikelets flat, 4–7(–9) mm wide, usually with 4–7 florets. Moist forests, swamps, and
prairie openings, sandy soils; Pineywoods and Post Oak Savannah, also Dallas Co. (Turner et al.
2003) to the w; also n Gulf Prairies and Marshes; se U.S. from VA s to FL w to OK and TX. Jun–
Nov. [C. laxum subsp. sessiliflorum (Poir.) L.G. Clark, C. laxum var. sessiliflorum (Poir.) Wipff &
S.D. Jones, Uniola sessiliflora Poir.] This taxon has been variously treated taxonomically. It has
been recognized as a separate species (e.g., Kartesz 1999), as a subspecies of C. laxum (e.g., Clark
1990; Yatskievych 1999), as a variety of C. laxum (e.g., Wipff & Jones 1994 [1995]; Diggs et al.
1999), or as part of an undivided C. laxum (e.g., Hatch 2002). Clark (1990) indicated there is significant
overlap between the two taxa in a number of morphological characters and that they
are almost completely sympatric; he concluded that they are not worthy of recognition as species.
Recently, Sánchez-Ken and Clark (2003) treated the two at the species level and gave a
number of morphological characters (used in the key above) by which to distinguish them.
Even though sympatric, the differences between them seem to be maintained. Additionally,
Sánchez-Ken and Clark (2003) noted that, while growing in similar habitats, C. sessiliflorum
extends “further into sphagnous stream heads, pine flatwoods, and pine savannahs.” Because of
these morphological and ecological differences, we are following Sánchez-Ken and Clark (2003)
in treating C. sessiliflorum as a separate species.
CHLORIS Sw. WINDMILL GRASS
Annuals or perennials; leaf sheaths strongly compressed and sharply keeled; ligule a ciliate membrane;
branches of inflorescence digitately or subdigitately arranged at tip of culm (apparently in
1 whorl) or else in several whorls; spikelets in 2 rows along 1 side of the branch axes, with 1(–2)
perfect floret at base and 1 or more reduced ones above, laterally compressed, disarticulating
above the glumes; glumes shorter than fertile floret; lemma of perfect floret usually awned, marginally
often variously and sometimes conspicuously pubescent; reduced florets without paleas.
AA C4 genus of 55–60 species (Barkworth 2003b) of tropical and warm areas of the world
(most abundant in the s hemisphere). The genus includes some fodder and pasture grasses, as
well as a number of significant weeds (Watson & Dallwitz 1992). Recent molecular studies
(Hilu & Alice 2000, 2001) raise questions about the monophyly of Chloris as traditionally delimited.
Enteropogon, UMBRELLA GRASS, here treated as a separate genus following Barkworth
(2003b), is sometimes included in Chloris (e.g., Correll & Johnston 1970; Gould 1975b; Hatch et
al. 1990). The most reliable character in separating the two genera is compression of the spikelets:
dorsally compressed in Enteropogon versus laterally compressed in Chloris (Jacobs &
Highet 1988). Molecular data link Chloris, Cynodon, Enteropogon, and Eustachys but do not
support combining the genera (Hilu & Alice 2000). Intergeneric hybrids of Chloris with
Cynodon are known (Watson & Dallwitz 1992). The following treatment draws heavily on
Gould (1975b). (Named for Chloris, Greek mother of Nestor, goddess of flowers) (subfamily
Chloridoideae, tribe Cynodonteae)
REFERENCES: Nash 1898; Clayton 1967a, 1982; Lazarides 1972; Anderson 1974; Gould 1975b;
Varadarajan & Gilmartin 1983a, 1983b; Jacobs & Highet 1988; Hilu & Alice 2000, 2001;
Barkworth 2003b.
1. Branches of inflorescence in 2–5 whorls along a main axis usually 20 mm or more long; reduced
(neuter or staminate) floret 1 per spikelet, truncate ____________________________________ C. verticillata
1. Branches of inflorescence usually in only 1 whorl, or appearing so (if in more than 1 whorl, then
the whorls crowded along an axis less than 20 mm long); reduced floret(s) 1–4 per spikelet,
truncate or not so.
2. Reduced floret 1 per spikelet; including species widespread and common in East TX.
3. Inflorescence branches bearing spikelets to very base; lowest spikelets of branch typically
less than 3 mm apart.