Isoëtes lithophila
Isoëtes lithophila N. Pfeiff
(Greek: lithos, rock and philos, love)
Local names: rock quillwort
Leaves typically 3–12 (–20+) cm long, erect, not or only slightly twisted, bright green, the outer surfaces pale toward base; velum covering the entire sporangium; megaspores gray to gray-brown or bronze, 0.25–0.40 mm in diam., the surfaces not cobwebby, microscopically smooth to obscurely tuberculate; 2n = 22 (Taylor et al. 1993). Temporary vernal pools on granite or gneiss outcrops in the Llano Uplift area of c TX in Burnet (V.L. Cory 49507, S.D .Jones et al. 10051, BRIT, det. W.C. Holmes, G.M. Soxman 448, TEX-LL, det. Holmes & Singhurst, SEM at TEXLL), Mason (S. & S. Pence 67, BRIT, det. W.C. Holmes), Llano (W. Krodel et al. 17t278, BRIT, det. W.C. Holmes, H. Bold s.n. , 1963, TEX-LL, det. Holmes & Singhurst), and Gillespie (Poole et al. 2002, 2010) cos.; endemic to c TX (Kartesz 1999; Carr 2002b, 2002c). Sporulating late winter–Jun. Poole et al. (2007a) discussed it in detail and noted that the epithet is often erroneously spelled “lithophylla.” This rare species is one of only two pteridophytes endemic to TX (the other is I. texana). It is also one of only two pteridophytes included in Rare Plants of Texas (Poole et al. 2007a). (Conservation Concern—TOES 1993: V; Poole et al. 2007a, 2007b, 2010: G2S2)