Cystopteris protrusa

Cystopteris protrusa (Weatherby) Blasdell
(Latin: protrusus, protruding, pushed out, or exserted, in reference to the rhizome apex extending beyond the point of leaf attachment)

Local names: southern bladder fern, lowland bladder fern, lowland brittle fern

Terrestrial; rhizomes protruding 1–5 cm beyond attachment of current season’s leaves, with tan to light brown or golden hairs as well as scales; leaves seasonally somewhat dimorphic, clustered, erect to erect-spreading, to 45 cm long; petioles usually green to straw-colored, even near base; leaf blades 1-pinnate-pinnatifid to 2-pinnate, ovate-lanceolate to elliptic, widest at or just below middle, to ca. 25 cm long and 12 cm wide, apically broadly acute, the ultimate segments dentate to serrate; earliest leaves small, sterile, coarsely divided, with rounded teeth marginally; later leaves larger, fertile, more finely divided, with sharply pointed teeth marginally; sori on veins of ultimate leaf segments (= smallest subdivisions of leaf); indusia lacking glandular hairs; 2n = 84 (Haufler et al. 1993). Moist deciduous forests; Gonzales Co. in the s Blackland Prairie (H.B. Parks s.n., Jan 1939, TAES) (cited by Correll [1956] as C. fragilis var. protusa), Harrison (Ajilvsgi 4065, BRIT—annotated by J. Peck) and Houston (Turner et al. 2003) cos. in the Pineywoods; also Victoria Co. (Turner et al. 2003) in the Gulf Prairies and Marshes. Cystopteris protrusa is also known from McCurtain Co., OK, just n of the Red River (Taylor & Taylor 28956, BRIT). Although the range map in Haufler et al. (1993) does not include TX and the species is apparently quite rare in the state, it is known from several TX localities; e U.S. from NH s to FL w to MN, NE, OK, and TX (the TX populations are disjunct to the sw of most of the range of the species); also Ontario, Canada. Sporulating spring–summer. [C. fragilis (L.) Bernh. var. protrusa Weatherby] Weakley (2010) noted, “This species is a diploid involved in the reticulate evolution of Cystopteris in e. North America.” The Gonzales Co. location is from the Ottine wetlands—a relict spring-fed ecosystem. Numerous other mesic species are disjunct to similar wet microhabitats in otherwise rather dry inhospitable environments in c TX, and are thought to be relicts of Ice Age times (see page 36). An Edwards Co. collection of C. reevesiana (Cory 35636, Devil’s Sink Hole, TAES) was incorrectly identified and mapped as C. protrusa by Diggs et al. (2006). The terrestrial habit, and rhizomes with tips protruding beyond attachment of leaves and with hairs as well as scales (other TX species usually on rocks and lacking rhizome hairs), distinguish C. protrusa from other TX members of Cystopteris (Haufler et al. 1993). This species is very similar in general morphology to Woodsia obtuse, blunt-lobe woodsia, and can be confused with that much more common species in the e 1⁄2 of TX. The two can be distinguished by the indusia, by the ultimate leaf segments which are not significantly narrowed at base in W. obtuse (versus obviously narrowed towards base in C. protrusa), and other characters (e.g., whether veins reach leaf margins) as given in the key separating Woodsia and the superficially similar Cystopteris in the family treatment of Woodsiaceae on page 307. This species was one of the first ferns for which trophopods (see genus description) were described (Wagner et al. 1970). Because of its rareness and limited distribution in the state, we consider this species to be of conservation concern in TX.

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