Isoëtes melanopoda

Isoëtes melanopoda J. Gay & Durieu ex Durieu
(Greek: melas, melanos, black, and pous or podium, foot)

Local names: black-foot quillwort

Leaves usually 15–40 cm long, erect, not or little twisted, often grass-green, the outer surface usually blackish and shiny toward very base (sometimes brownish or rarely pale); velum covering less than 3⁄4 of sporangium; megaspores white, 0.25–0.45 mm in diam., the surfaces not cobwebby, microscopically with obscure sparse ridges; 2n = 22 (Taylor et al. 1993). Seasonally saturated soils, temporary or shallow pools, usually on non-calcareous substrates (Taylor et al. 1993); widely scattered in e . of TX (e.g., Madison Co., A.K. Neill 2545, BRIT) (including far East TX (e.g., Hardin, Sabine, and Shelby cos., BAYLU; Holmes et al. 2005) where it has often been “overlooked” (Holmes et al. 2005); Pineywoods and n Gulf Prairies and Marshes w to Cross Timbers and Prairies and e Edwards Plateau; e U.S. from NJ s to GA w to NE and TX, also UT. Sporulating Mar–Oct. This species commonly has black and shiny phyllopodia (= hardened, sclerified leaf bases) persisting from the previous year (Heafner & Bray 2005). Brunton and Britton (2006) recently named a new subspecies of I. melanopoda (subsp. silvatica) that occurs in the e U.S. from NJ s to AL and w to MS and TN; TX populations are of subsp. melanopoda. Subspecies silvatica typically has wider leaves (average 1.5–2.18 mm wide vs. 0.51–1.1 mm), pale leaf bases (vs. black), larger megaspores with bolder ornamentation and habitat preference for deciduous woodland swamp (vs. open grassland/prairie).

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