Isoetes luetzelburgii U. Weber, 1922

De Souza Pereira, Jovani B., Silvestre, Leandro C. & Santiago, Augusto C. P., 2018, Lectotypification and observations on the morphology, distribution and conservation status of Isoetes luetzelburgii (Isoetaceae), Phytotaxa 364 (3), pp. 289-295 : 290

Isoetes luetzelburgii U. Weber in Estud. Bot. Nordeste 3: 257. 1926

Lectotype (M!, M0210646!, designated here), isolectotype (M!, M0210647!, designated here): — BRAZIL. Parahyba do Norte (Paraíba): Serra Borborema, Lagoa dos Patos, July 1921, Luetzelburg 13709.

Nomenclature:— Ulrich Weber described Isoetes luetzelburgii and indicated the type in herbarium “Bras” in the protologue of the name referring that this collection was part of Flora Brasiliensis. The type (Luetzelburg 13709) was subsequently deposited in M along with specimens from several other plant groups of the Flora Brasiliensis. Weber confirmed the presence of the “ holotype ” in M in his study published in 1934 ( Weber 1934). Despite this, Fuchs-Eckert raised doubt about the provenance of the “ holotype ” by labelling “ isotype ” on the herbarium sheets of Luetzelburg 13709 in M, a mistake he later corrected ( Fuchs-Eckert 1982). The type (Luetzelburg 13709) collection is mounted in two herbarium sheets (each one of them composed of a single specimen divided in two halves). Because neither herbarium sheet was designated in the protologue of the name nor appropriately annotated on the herbarium sheets, it is impossible to know if one or the other of the two sheets is the “ holotype ”. Accordingly, lectotypification is required.

The following provides a detailed description of Isoetes luetzelburgii based on our examination of the herbarium material cited below. This is considerably more informative than has previously been available in the protologue of the name.

Description:— Corm globose, 0.5 – 2.5 cm wide, 3 - lobate. Leaves 0.6–1.5 mm wide, 8–60 cm long, 15–95 per individual, linear, slightly flexuous, laxly ascending to recurved, apex attenuate; alae 1–2 mm wide at the sporangium, 3.5–13 cm long, extending from the base 1/5–1/4 toward the apex, hyaline or light brown, membranaceous, apex attenuate. Subula olive green, trigonal, with four well developed fiber bundles. Labium present, persistent, cordate, 1–3.5 × 2–5 mm. Ligule only observed in fixed material, 1.8–2.7 × 1.4–1.8 mm, hyaline, deltoid. Velum rudimentary, ca. 0.2 mm wide along the lateral edges of the sporangium. Sclerified phyllopodia present. Sporangium 5–10 × 3–4.5 mm, oblong, brown or dark brown, concolor, at the base of the leaf. Megaspores white, not lustrous, irregular in size, 308–490 μm in diameter; macro-ornamentation in the proximal and distal surface verrucate; laesures distinct, wider than higher, with convex sides, apex rounded, truncate, or emarginate; equatorial ridges low, obscure. Microspores 27–32 μm long, light grey, varying from obscurely rugulate (almost plain) to sparsely low echinate-tuberculate.

Examined materials:— BRAZIL. Bahia: Marcolino de Souza, 11 February 1997, Giulietti 5501 (K!, CEPEC!). Paraíba: Serra Borborema , Lagoa dos Patos, Jul 1921, Luetzelburg 13709, 12011 (M!) ; Souza, São Gonçalo , 01 April 1936, Luezelburg 27091 ( IPA!) ; São José de Espiranhas, Fazenda Vale da Sela, 12 June 2014, Silvestre 48 (ALCB!, UFRN!). Pernambuco: Parnamirim , Fazenda Travessia , 15 June 1984, Araújo 148 ( IPA!) ; Caruaru, Serra do Medo, 500 m, 24 February 2014, Santiago 1286 ( UFP!). Rio Grande do Norte: Serra Negra do Norte , Estação Ecológica do Seridó , 8 July 2006, Queiroz 1075 ( UFRN!) ; idem for 5 April 2018, Pereira & Guimarães 1082 ( MG!) .