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

ASPLENIUM L. SPLEENWORT
ASPLENIUM/ASPLENIACEAE
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East TX species terrestrial or on rocks; stems (rhizomes) short-creeping to erect; leaves clustered,
1-pinnate, monomorphic or slightly dimorphic, mostly evergreen; pinnae auricled basally,
the auricle on the acroscopic side (= side toward the leaf apex) of the pinnae; sori elongate
along veins; indusia attached along one edge of the sori.
AA large and diverse, cosmopolitan genus of ca. 700 species (following Wagner et al. 1993) of
terrestrial, epipetric (= on rocks), and epiphytic species. This is one of the largest genera of ferns,
and the species range in size from those with leaves only a few centimeters long to the giant
BIRD’S-NEST FERNS, with leaves more than 1 m long (Hoshizaki & Moran 2001). The genus is well
known for its interspecific hybridization and complex polyploid series with numerous allopolyploids.
Ploidy levels range from diploid to hexaploid, and three-fifths of the species are
thought to be of hybrid, allopolyploid origin. A number of species are cultivated as ornamentals
(e.g., A. nidus L.—BIRD’S-NEST FERN). (Greek: splen, spleen; thought by Dioscorides, Greek
naturalist of the first century A.D., to be useful for treating spleen diseases)
REFERENCES: Wagner 1954; Correll 1956, 1966a; Wagner & Johnson 1981, 1983.
1. Pinnae (leaflets) usually alternate, with their basal auricles overlapping the rachis, their margins
subentire to deeply serrate or incised; plants terrestrial or growing on rocks; leaves slightly dimorphic,
the fertile erect, the sterile smaller and spreading _____________________________ A. platyneuron
1. Pinnae opposite, usually not overlapping the rachis, their margins subentire to crenulate; plants
usually growing on rocks; leaves monomorphic, all fertile, erect or ascending _________________ A. resiliens
Asplenium platyneuron (L.) Britton, Sterns, & Poggenb., (broad-nerved, apparently based on an
inaccurate early drawing—Nelson 2000), EBONY SPLEENWORT, BROWN-STEM SPLEENWORT,
INDIAN-HAIR FERN. Leaves to 50 cm tall; leaf blades linear-lanceolate to narrowly elliptic-lanceolate
in outline; petiole and rachis usually reddish brown to dark brown (rarely nearly black),
shining. Sandy, moist, wooded banks and slopes, or on rocks; Pineywoods and Gulf Prairies and
Marshes w to West Cross Timbers; se Canada and throughout e U.S. w to MN and AZ. Sporulating
Apr–Dec. [A. platyneuron var. bacculum-rubrum (Fernald) Fernald] Two varieties are sometimes
recognized in this species (e.g., Kartesz 1999). However, we are following Wagner and
Johnson (1983), Wagner et al. (1993) and Yatskievych (1999) in not recognizing infraspecific
taxa. According to Correll (1956), “… this is one of the commonest woodland ferns occurring in
eastern Texas. It may be found not only as a solitary plant but also in extensive stands.” Wagner
et al. (1993) indicated that this species “… is remarkable in that it occurs in southern Africa as
well as in North America. No other North American fern has this distribution.” The species is
also unusual in possessing trophopods; these modified petiole bases accumulate food reserves
and persist after withering of the leaf blade (Wagner & Johnson 1981, 1983; Nauman et al.
2000). m/276
Asplenium resiliens Kunze, (resilient, springing or bending back), LITTLE EBONY SPLEENWORT,
BLACK-STEM SPLEENWORT. Leaves to ca. 35 cm tall, the blades linear-oblong to linear-lanceolate
in outline, usually more coriaceous than in A. platyneuron; petiole and rachis black, shining.
Usually growing on rocks; Bell, Grayson, Travis (BRIT), Bexar (TAES), Angelina, Bastrop, Comal,
Hays, Orange, and Williamson (Turner et al. 2003) cos.; widely scattered in TX but primarily w
2/3; across s 1/2 of U.S. from PA s to FL w to NV and AZ. Sporulating Apr–Nov. This species is
apogamous (= a type of asexual reproduction that does not involve fertilization; the sporophyte
is formed directly from the gametophyte without gamete production), an adaptation for xeric
environments (J. Peck, pers. comm.).