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

680 HYPOXIDACEAE/HYPOXIS
AA primarily s hemisphere genus of 100 species (Herndon 2002) found in Africa, North
America, South America, s Asia, Australia, and especially s Africa (Judd 2000). Nordal (1998)
suggested that the number of species is uncertain because of the presence of apomictic forms.
The group is taxonomically difficult, and observation of seed characters under magnification is
“often required for definitive identification” (Judd 2000). Herndon (1992a) noted that the difficulty
is due to “phenotypic plasticity combined with the similarity in size and general appearance
of all North American species.” In addition, species concepts within the genus are unsettled—e.g.,
the status of H. longii (here synonymized with H. sessilis). This is partly due to the
fact that Hypoxis species show significant morphological variability associated in part with
whether at any given time chasmogamous or cleistogamous flowers are being produced (Herndon
1988). Some authorities (e.g., Britt 1967; Radford et al. 1968) indicated that the species included
here are poorly defined and perhaps all belong to a single polymorphic species; however,
we are following Herndon (2002) in recognizing five species in East TX. Some species (e.g., H.
sessilis) have adapted to periodic burning and bloom most actively after their habitat has been
burned; this may be the result of increased light levels and/or an increase in nutrient availability
(Herndon 1988). Flowers typically open soon after sunrise and close by noon or shortly after
(Herndon 1988, 1992a, 1992b). The following key to species is modified from Herndon (2002).
(Old name taken over by Linnaeus; Greek: hypo, beneath, and oxys, sharp, in reference to the
base of the capsule)
REFERENCES: Brackett 1923; Britt 1967; Taylor & Taylor 1977, 1981b; Godfrey & Wooten 1979;
Herndon 1988, 1992a, 1992b, 2002.
1. Leaves glabrous or nearly so; seeds black, lustrous.
2. Pedicels usually twice as long as bracts or longer, usually 9–25 mm long; ovary obconic, densely
pubescent; tepals much longer than ovary; capsules only slightly longer than wide, 2–6 mm
long; flowers usually (1–)2–5(–7) per inflorescence, in a � umbellate arrangement, the
proximal 2 flowers paired _________________________________________________________ H. hirsuta
2. Pedicels usually shorter than bracts, usually 12 mm or less long; ovary cylindric, glabrate to
sparsely pubescent; tepals at most twice as long as ovary; capsules usually much longer than
wide, 5–10 mm long; flowers 1–3(–7) per inflorescence, the proximal 2 flowers (if 2 or
more present) not paired ________________________________________________________ H. curtissii
1. Leaves sparsely to densely pubescent to pilose; seeds black and lustrous to dull and brown to
iridescent.
3. Pedicels usually twice as long as bracts or longer; flowers usually (1–)2–5(–7) per inflorescence,
in a � umbellate arrangement, the proximal 2 flowers paired _______________________ H. hirsuta
3. Pedicels usually less than twice as long as bracts; flowers usually 1–2(–4) per inflorescence,
the proximal 2 flowers (if 2 or more present) not paired.
4. Pedicels usually longer than bracts; tepals longer than pedicel; anthers 1.5–3.5 mm long;
seeds black, lustrous; bases of old leaves disintegrating into persistent bristly fibers __________ H. rigida
4. Pedicels shorter than to longer than bracts; tepals shorter than to longer than pedicel;
anthers 0.6–2.2 mm long; seeds either iridescent OR dull, brown; bases of old leaves not
becoming bristly fibrous OR sometimes disintegrating into bristly fibers.
5. Tepals 1.5–2 times as long as ovary; seeds iridescent, black beneath a film or coating of
a golden-brown iridescent substance; pedicel usually slightly shorter than to as long as
bracts ____________________________________________________________________ H. sessilis
5. Tepals less than 1.5 times as long as ovary; seeds dull, brown, not iridescent; pedicel
usually longer than bracts ___________________________________________________ H. wrightii
Hypoxis curtissii Rose, (for A.H. Curtiss, 1845–1907, collector of the type specimen), SWAMP YEL-
LOW STAR-GRASS, COMMON YELLOW STAR-GRASS, CURTISS’ YELLOW STAR-GRASS, CLUBPOD
GOLDSTAR. Plant similar to H. hirsuta; leaves glabrous or nearly so, 3–12 mm wide; inflorescence
with 1–3(–7) flowers, the proximal 2 flowers (if 2 or more present) not paired; capsule 5–10 mm