Selaginella apoda

Selaginella apoda (L.) C. Morren var. apoda
(Greek, a-, without, and pous or podium, foot, = footless, in reference to “the stalkless strobili, which were noteworthy in Lycopodium, the genus in which Linnaeus originally place this species”—Thieret 1980)

Local names: meadow spike-moss, basket selaginella

Plant prostrate-creeping or ascending annual (all other TX species are perennial), often forming mats, delicately thin-herbaceous (our only such species); leaves in 4 ranks, of 2 distinct kinds, without significant hyaline margins, the two types of leaves different in size and shape—lateral leaves ovate to ovate-elliptic, asymmetrical, ca. 1.35–2.25 mm long, 0.75–1.35 mm wide; appressed-ascending (medial) leaves lanceolate, smaller, to ca. 1.2(–1.6) mm long; strobili solitary or paired, obscurely quadrangular (= 4-sided)-flattened, 0.5–2 cm long; 2–4 mm in diam.; sporophylls apically acute to acuminate. Moist areas, ditches, stream banks, seeps, low fields, and low woods; widespread in Pineywoods (e.g., E. Whitehouse 23088, BRIT), Post Oak Savannah, n Gulf Prairies and Marshes and disjunct to e Edwards Plateau (e.g., Burnet Co., Correll & Correll 12746, BRIT, TEX-LL); e U.S. from ME s to FL w to IL, OK, and TX; also disjunct to the mts. of s Mexico and Guatemala. Sporulating May–Dec. [Diplostachyum apodum (L.) Beauv., Lycopodium apodum L., not S. apoda (L.) Spring (a superfluous name—see discussion below)] In flood-prone bottomlands in East TX this species is sometimes epiphytic on the often moist lower parts of tree trunks (J. Stanford, pers. comm.). A variety of S. apoda, var. ludoviciana (A. Braun) B.F. Hansen & Wunderlin (based on S. ludoviciana (A. Braun) A. Braun), occurs in the Gulf coastal plain (Hansen & Wunderlin 1998). That variety, which differs in minor ways (e.g., hyaline leaf margins) from var. apoda, is known from GA, FL, AL, MS, and se LA. Selaginella apoda has an interesting biogeography. It is one of numerous TX species that have widespread populations in East TX and isolated disjunct populations on the Edwards Plateau (see discussion on page 37). The range map in Valdespino (1993; and on U.S. map provided here) also shows a disjunct occurrence in s TX (which we have not been able to confirm). Even more interesting it is one of a few species and numerous deciduous forest genera that occur broadly across the eastern United States as far west as TX, and then reappear disjunctly in the mountains of Mexico and in some cases even in Guatemala; see Fig. 40 and page 37 for a possible explanation of this distribution. Selaginella apoda is being considered as a model species for experimental work on lycophytes because of its short life cycle (85 days from spore to spore) and ease of cultivation (Schulz et al. 2010a, 2010b). Reveal and Gandhi (2012) recently published an article discussing technical nomenclatural problems associated with the name Selaginella apoda (L.) Spring—there has been disagreement about the correct name for this species for decades (e.g., Morton 1967). They argued, based on rules of the International Code of Botanical Nomenclature, that the correct name is Selaginella apoda (L.) C. Morren. Because of their arguments and because the name S. apoda (L). C. Morren is now being accepted by most botanical authorities (e.g, IPNI [International Plant Names Index] 2012; TROPICOS 2012), we are following their recommendation.

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