Ceratopteris thalictroides
Ceratopteris thalictroides (L.) Brongn.
(resembling Thalictrum, meadow-rue, in the Ranunculaceae, and Greek: -eides, -oides, like)
Local names: water sprite, water fern
Plant short-lived, aquatic or semiaquatic, usually rooting, but sometimes floating; leaves dimorphic, with adventitious buds or small plantlets in notches along margins; sterile leaves 1–3 pinnate, the blades lanceolate to ovate or deltate in outline, 2–41 cm long, 2–20 cm wide, with relatively broad ultimate segments (broader than the linear ultimate segments of the fertile leaf blades), firm, the petioles 1–31 cm long, not inflated; fertile leaves 3–4 pinnate proximally, 2-pinnate distally, larger than the sterile leaves, 2–117 cm long, to 48 cm wide, the blades lanceolate to ovate, deltate, or cordate in outline, finely dissected with the ultimate segments linear, the petioles 1–46 cm long; margins of fertile blades revolute, covering the 1–3 rows of sporangia and forming false indusia; 2n = 154, 156 (tetraploid) (Masuyama & Watano 2005). Cultivated in aquaria and warm-weather lily or fish ponds and presumably escaping; usually rooted in mud in quiet or moving water of springs and adjacent rivers and lakes; Comal (P.A. Amerson 2973, 2080, BRIT, Petrik-Ott & Ott 1003, TAES), Hays (P.A. Amerson 2087, BRIT; Correll & Correll 38315, TEX-LL; S.A. Conry 41, BAYLU), and Bell (Petrik-Ott & Ott 1004, TAES, US—Petrik-Ott & Ott 1976) cos. along the Balcones Fault at the edge of the Blackland Prairie and the Edwards Plateau. According to D. Lemke (pers. comm. 1998), at that time it was still present in the San Marcos River in Hays Co. Petrik-Ott and Ott (1976) suggested that the constant temperature of the springs along the Balcones Fault may allow this mainly tropical species to persist indefinitely in TX. The species was first reported from TX by Morton (1967a) and was apparently introduced to the state in 1963 (Hannen 1969). Sporulating Mar–Oct. Native to tropical areas worldwide, except Africa, it has been found escaped in the U.S. in CA, FL, LA, TX (Lloyd 1993), and MS (Kartesz 1999); also s Mexico. [Acrostichum thalictroides L.] This is an extremely widespread and variable species (Lloyd 1974). Based on molecular work and breeding studies, Masuyama et al. (2002), Masuyama and Watano (2005), Adjie et al. (2007), and Masuyama (2008) found there are at least three morphologically very similar cryptic species hidden within C. thalictroides (“north type,” “south type,” “third type”). Apparently there is reticulate evolution with the three cryptic species having independent allopolyploid origins, with contributions variously from the Old World diploid C. cornuta and two hypothetical diploid ancestors. New World populations seem to be of the “south type” (Masuyama et al. 2002). Ceratopteris thalictroides is cultivated in some areas (e.g., Japan) as a spring vegetable in flooded rice fields (Mabberley 1997). Tryon and Tryon (1982) suggested that although Ceratopteris is usually considered to be an annual, it “… may be more accurately described as short-lived.” They noted that many tropical habitats “… lack the seasonality necessary to provide a basis for an annual lifecycle.”