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

JUNCUS/JUNCACEAE
703
mainly in wet or damp habitats. The monotypic s African genus Prionium (woody trunk to > 1
m long, juncaceous flowers), which was previously treated in Juncaceae (e.g., Balslev 1998), is
now excluded based on molecular evidence (e.g., Plunkett et al. 1995; Munro & Linder 1998;
Chase et al. 2000). Pollination in the family is predominantly by anemophily (= wind-pollination);
specific adaptations for wind-pollination include many-flowered inflorescences, abundant
smooth pollen, and large stigmatic surfaces (Balslev 1998). While previously believed to be
associated with the Liliales (due to superficial resemblances), the family is now considered to
be related to the Cyperaceae (e.g., Dahlgren et al. 1985; Duvall et al. 1993b; Simpson 1995; Chase
et al. 2000) and more distantly to other families of the Poales, including Poaceae and Xyridaceae
(Chase et al. 2000). In fact, some molecular data suggest that Juncaceae and Cyperaceae are sister
taxa (Chase et al. 1995b; Linder & Kellogg 1995), or even that Cyperaceae may be derived
from within Juncaceae, possibly making Juncaceae paraphyletic (Plunkett et al. 1995; Munro &
Linder 1998). According to Plunkett et al. (1995), the “progenitor-derivative relationship of
Juncaceae and Cyperaceae … reveals an additional example of paraphyletic families which presents
a series of taxonomic dilemmas.” A number of similar situations exist (e.g., Brassicaceae
and Capparaceae, Cactaceae and Portulacaceae), and if paraphyletic families are disallowed (as
favored by many cladists), taxonomists are thus faced with wholesale rearrangement of many
long established and easily recognized families—see Appendices 5 and 6 for further discussion
of these issues. (subclass Commelinidae—Cronquist; order Poales—APG II)
FAMILY RECOGNITION IN THE FIELD: grass-like or sedge-like herbs with mostly basal, tufted, linear
leaves in (2–)3 ranks; flowers inconspicuous with 6 scaly perianth segments (= tepals), often clustered
but not in spikelets; fruit a capsule; the somewhat similar Poaceae and Cyperaceae have 1seeded
fruits, either lack a perianth or have the perianth very reduced, and have flowers in spikelets.
REFERENCES: Dahlgren et al. 1985; Plunkett et al. 1995; Simpson 1995; Balslev 1996, 1998; Munro
& Linder 1998; Brooks & Clemants 2000.
1. Plants glabrous; seeds numerous per capsule; capsules usually 3-celled (sometimes imperfectly
so); leaf blades terete (= rounded in cross section) or flat; leaf sheaths open ______________________ Juncus
1. Plants with pubescence; seeds 3 per capsule; capsules 1-celled; leaf blades flat; leaf sheaths closed
___________________________________________________________________________________ Luzula
JUNCUS L. RUSH
Glabrous perennial or annual (only 2 East TX species) herbs with fibrous roots, many species
rhizomatous; leaf blades flat or terete, sometimes septate (= with internal cross-partitions
sometimes resulting in conspicuous ring-like bands visible externally); leaf sheaths open; inflorescences
variable, sometimes with numerous rebranched branches, terminal or appearing
lateral; flowers solitary on pedicels or often in head-like clusters; capsules usually 3-celled
(sometimes imperfectly so and thus apparently unilocular); seeds numerous.
AA genus of ca. 300 species (Brooks & Clemants 2000), cosmopolitan in distribution but rare
in the tropics. Because inflorescence, flower, and fruit characters are widely used in the following
key, fertile specimens are essential for accurate identifications. Some species (e.g., J. effusus and J.
squarrosus L.) have been used in making baskets and chair bottoms (Judd et al. 1999). (Latin:
iuncus, name for rush; derived from iungere, to join or bind, from use of the stems for tying)
REFERENCES: Engelmann 1868; Wiegand 1900; Fernald & Wiegand 1910; Eleuterius 1975, 1978;
Hermann 1975; Hämet-Ahti 1980; Catling & Spicer 1987; Brooks 1989; Snogerup 1993; Brooks &
Whittemore 1999; Kirschner et al. 1999.
1. Inflorescence appearing lateral (= appearing to originate from the side of the “stem”), the “stem”
apparently continuing beyond it (actually the “stem” beyond the inflorescence is a stem-like
involucral bract and the inflorescence is thus pseudolateral); leafy bracts (other than the stemlike
bract) absent or much shorter than inflorescence.