Selaginella sematophylla Valdespino, G. Heringer & Salino, 2015

Valdespino, Ivan A., Heringer, Gustavo, Salino, Alexandre, Goes-Neto, Luiz A. de Araujo & Ceballos, Jorge, 2015, Seven new species of Selaginella subg. Stachygynandrum (Selaginellaceae) from Brazil and new synonyms for the genus, PhytoKeys 50, pp. 61-99 : 77-80

Selaginella sematophylla Valdespino, G. Heringer & Salino sp. nov. Figures 14 , 15

Diagnosis.

Selaginella sematophylla differs chiefly from Selaginella vestiens in having (vs. lacking) idioblasts on upper surfaces of median leaves and dorsal sporophylls and on lower surfaces of lateral leaves, and by its acute (vs. acuminate to aristate, 0.4-0.7 mm) median leaves, and creeping (vs. ascending to suberect) habit.

Type.

BRAZIL. Minas Gerais: São Sebastião do Paraíso, Baú, [ca. 20°53'52"S, 46°57'33"W], 26 Apr 1945, A.C. Brade & A. Barbosa 17953 (holotype: MO!; isotypes: BM!, CESJ!, NY!, PMA-fragment!, RB-image!).

Description.

Plants terrestrial. Stems creeping, stramineous, 2-3.5 cm long, 0.1-0.3 mm diam., exarticulate, not flagelliform or stoloniferous, 1-branched. Rhizophores axillary, borne throughout stems, filiform, 0.05-0.1 mm diam. Leaves heteromorphic throughout, thin-membranaceous to chartaceous, both surfaces glabrous, upper surfaces green, lower surfaces silvery green. Lateral leaves distant or imbricate distally, patent, ovate, 1.0-1.4 × 0.6-0.9 mm; bases rounded, acroscopic bases strongly overlapping the stems, basiscopic bases free from the stems; acroscopic margins hyaline to green-hyaline in a band 2-6 cells wide, the cells elongate and papillate parallel to margins, papillae in 1 row over each cell lumen, short- to long-ciliate along proximal ¼-½ and serrulate distally; basiscopic margins hyaline in a band 2 or 3 cells wide, the cells as on acroscopic margins, short-ciliate along proximal ⅕, otherwise serrate to serrulate along distal ⅘; apices acute, tipped by 1-3 teeth; upper surfaces comprising quadrangular to rounded, sinuate-walled cells, some of these on or near basiscopic and apical regions of the laminae, which are covered by 1-5 papillae, without idioblasts or stomata, lower surfaces comprising elongate, sinuate-walled cells, some of these papillate and idioblast-like, papillae in 1 row over each cell lumen, with stomata along midribs and few irregularly distributed over laminae. Median leaves imbricate, ascending, lanceolate, 0.8-1.4 × 0.3-0.7 mm; bases oblique to rounded, margins hyaline in a band 3-7 cells wide, the cells elongate and papillate parallel to margins, papillae in 1 row over each cell lumen, serrate to denticulate throughout; apices acute, tipped by 1 or 2 teeth; upper surfaces comprising rounded to quadrangular, sinuate-walled cells, most of these covered by 1-7 papillae, and some idioblast-like, papillate, elongate cells with papillae in 1 row over each cell lumen along both sides of the midribs, with stomata in 1 or 2 rows along midribs and a few irregularly distributed on proximal region of inner half of the laminae, lower surfaces comprising elongate, sinuate-walled cells, without stomata. Axillary leaves similar to lateral leaves. Strobili terminal on branch tips, lax, slightly quadrangular, 2.0-8.0 mm. Sporophylls monomorphic to slightly dimorphic, without a laminar flap, lanceolate, 1-1.4 × 0.5-0.8 mm, each without a keel; bases rounded; margins hyaline, serrulate; apices gradually acute, tipped by 1-3 teeth; dorsal sporophylls with both surfaces having idioblasts, upper surfaces green with cells as in median leaves, except for the half that overlaps the ventral sporophylls, there hyaline to greenish hyaline and with elongate, papillate, and slightly sinuate-walled cells, lower surface silvery green comprising elongate, sinuate-walled cells; ventral sporophylls with both surfaces hyaline and comprising elongate, sinuate-walled cells. Megasporangia in 2 ventral rows; megaspores cream or light-yellow, rugulate-reticulate with granulate-perforate microstructure on proximal faces, reticulate or reticulate-granular with granulate-echinulate and perforate microstructure on distal faces, 275-290 µm. Microsporangia in 2 dorsal rows; microspores orange, psilate marginally to rugulate towards the center with granulate microstructure on proximal faces, rugulate-cristate or cristate with broad baculate-like projections and granulate microstructure on distal faces, 28-40 µm.

Habitat and distribution.

Selaginella sematophylla is known from Minas Gerais, Espírito Santo, and Rio de Janeiro states in Brazil. It grows in Campos Rupestres and Atlantic Rainforest vegetation on sandy soil in shaded, wet places at 1000-1230 m.

Etymology.

The epithet of the new species derives from the Greek, sema -tos, meaning sign, flag, mark and phyllon, meaning leaf; this refers to the presence of conspicuous, hyaline idioblasts on upper leaf surfaces.

Conservation status.

The distributional range of Selaginella sematophylla encompasses three southeastern states of Brazil, but the vegetation types it inhabits are in peril; thus, we believe advisable to consider it vulnerable (VU), according to IUCN (2012) categories and criteria.

Additional specimens examined (paratypes).

BRAZIL. Minas Gerais: Arredores de São Sebastião do Paraíso, Apr 1945, Brade et al. [Beta 109] (R); Baú, 26 Apr 1949, Brade 3461 (CESJ); Serra Nova, Rio Pardo de Minas, Parque Estadual de Serra Nova, 15°39'37,5"S, 42°45'53,7"W, 1000-1230 m, 13 Mar 2007, Salino et al. 11734 (BHCB). Espírito Santo: Santa Maria do Jetibá, Garrafão, Pedra do Garrafão, 20°10'24,5"S, 40°55'6,8"W, 1081 m, 28 Aug 2009, Salino et al. 14543 (BHCB, PMA). Rio de Janeiro: Santo Antônio do Imbé, Mandigueira, Apr 1932, Brade & Santos-Lima 11670 (R).

Discussion.

Selaginella sematophylla is a member of subg. Stachygynandrum and is characterized by having stems 1-branched, lateral and median leaves with hyaline margins, and idioblasts on upper surfaces of median leaves (Fig. 14A, B ), lower surface of lateral leaves (Fig. 14C, D ), and on both surfaces of sporophylls.

In the past, specimens of Selaginella sematophylla were identified as Selaginella fragillima (= Selaginella vestiens , which see for discussion). Selaginella sematophylla differs from Selaginella vestiens by cell types on leaf surfaces, median leaf apex shape, and habit, as discussed in the diagnosis.

Figures

Figure 14. Selaginella sematophylla Valdespino, G. Heringer & Salino. A Section of upper surface of stem B Upper surface of median leaf C Section of lower surface of stem D Lower surface of lateral leaf A-D taken from paratype, Brade et al. [Beta 109] (R).

Figure 15. Selaginella sematophylla Valdespino, G. Heringer & Salino. A Megaspore proximal face B Close-up of megaspore proximal face surface C Megaspore distal face D Close-up of megaspore distal face surface E Microspore proximal face F Close-up of microspore proximal face surface G Microspore distal face H Close-up of microspore distal face surface A-H taken from holotype, Brade & Barbosa 17953 (MO).