Selaginella P . Beauv . from Minas Gerais , Brazil

Selaginella P. Beauv. is the only genus in the family Selaginellaceae Willk. The genus is monophyletic, has a cosmopolitan distribution, contains about 750 species and can be characterized by the presence of rhizophores, leaves, a ligule, heterospory and adaxial, reniform sporangia. Twenty species were found in the study area: Selaginella alstonii, S. contigua, S. convoluta, S. decomposita, S. erectifolia, S. erythropus, S. flexuosa, S. jungermannioides, S. macrostachya, S. marginata, S. microphylla, S. muscosa, S. producta, S. sellowii, S. sematophylla, S. suavis, S. sulcata, S. tenella, S. tenuissima and S. vestiens. Two new species records for the state are presented (S. jungermannioides and S. tenella). We present descriptions of the genus and species, an identification key, the synonyms pertaining to Brazil, illustrations, and comments about the taxonomy and distribution of species in Brazil.


Introduction
Selaginella is the only genus in the family Selaginellaceae, has a fossil record that dates back from the late Carboniferous (Rowe 1988;Thomas 2005) and is placed in the division Lycopodiophyta (Pryer et al. 2001;Banks 2009).The family is clearly monophyletic and is sister to Isoetaceae (Korall et al. 1999;Pryer et al. 2001;Korall & Kenrick 2002;Pryer et al. 2004).
Various works exist about the infrageneric classification of Selaginella (e. g. Spring 1849;Baker 1883;Walton & Alston 1938;Alston et al. 1981;Jermy 1986;1990).The most recent classifications (Jermy 1986;1990) divide Selaginella into five subgenera based on morphology and geographic distribution.Since then phylogenetic studies based on molecular characters have suggested that some of these subgenera may not be monophyletic (Korall et al. 1999;Korall & Kenrick 2002).Furthermore, Korall & Kenrick (2004) as well as the previously mentioned studies have suggested the infrageneric division of Selaginella into two groups: one group representing S. selaginoides (subg.Selaginella) and another group, with the majority of the species, called the "rhizophoric clade" by Korall & Kenrick (2002).

Materials and methods
The taxonomic study was based on samples collected by a team of pteridologists from UFMG, which were processed according to standard techniques and deposited at BHCB.In addition, herbarium specimens from Brazilian (CESJ, HUFU, OUPR, R, RB,, SP and SPF) and foreign herbaria (B, BM, C, F, K, NY and P) with important historial and type specimens, including digitized images, were studied.The herbarium abbreviations used in this work are based on Index Herbariorum (Thiers 2015).
The genus description was based on Tryon & Tryon (1982), Tryon & Stolze (1994), Fraile et al. (1995) and Mickel et al. (2004).Species descriptions were based on selected material and field observations.Measurements of leaves were made following Valdespino et al. (2014), whereas those of stems diameter were taken below the first branch and of the width of terminal branches on sterile branches (including leaves).Spore color given are based on observation under a dissecting scope with an incident yellow light at 6.7-80.0magnification and taking care that these were not contaminated by debris or fungi.The terms employed in this work are based on those used by Lellinger (2002), except for carinate (Stearn 1992) and isophyllous and anisophyllous (Mickel et al. 2004).Additionally, we prefer to follow Mital (1969) and Valdespino (1995) as explained in Valdespino et al. (2014) in terming leaves surfaces as "upper" (in lateral leaves = adaxial, while in median leaves = abaxial) and "lower" (in lateral leaves = abaxial, whereas in median leaves = adaxial).
Moreover, to keep descriptions manageable, the presence of idioblasts and other projections on leaf surfaces is only mentioned for those species where they are found.We present the discrepant morphological measures between parentheses to highlight the exception.
Key to the species of Selaginella that occur in Minas Gerais

Fig. 1O-R
Stem erect, greenish to stramineous, to 11 cm long, 0.4-0.7 mm diam., vascular bundle one; terminal branch 1.2-2.6 mm wide.Rhizophores ventral, present on lower ⅓ of stem, rarely on lower ½.Leaves anisophyllous, the lateral leaves at the base of the stem approximate to contiguous, less than 0.9 mm apart.Lateral leaves 1.1-2.1 x 0.5-1.0mm, ascending, slightly incurved at the apex, basifixed, ovate-lanceolate to oblong-lanceolate, base slightly rounded on acroscopic side, margin acroscopically serrate    Comments: Selaginella muscosa is characterized by its leaves with idioblasts on the upper surface, lateral leaves with a cordate base acroscopically and dorsal leaves with an aristate apex.Alston et al. (1981) pointed out that S. muscosa is a variable and possibly mixed species.Valdespino (1995) concluded that S. deltoides A. Braun and S. trifurcata Baker, which were subsumed under S. muscosa by Alston et al. (1981), were the same taxon but not closely related to or conspecific with the latter species.Valdespino (1995) did confirm, however, some incipient racial differentiation between specimens from the northern, middle, and southern part of the S. muscosa distribution range that merits further investigation.We observed also some variability among specimens found in Minas Gerais, which suggest this taxon might be a species complex.Comments: Selaginella sematophylla can be distinguished by its prostrate habit, lateral leaves oblong to ovate-oblong, dorsal leaves lanceolate with an acute apex, conspicuous hyaline margins and the presence of idioblasts on the adaxial surface.This species can be differentiated from S. vestiens because the latter has an erect habit, dorsal leaves with an acute to aristate apex and lacks idioblasts on the upper surface.In addition, S. sematophylla can be differentiated from S. jungermanioides since the latter has dorsal leaves that are ovate to ovate-lanceolate with an acuminate apex, and lacks idioblasts on the upper surface.Some specimens of S. sematophylla were identified as S. fragillima; however, after studying the type specimen of the latter species it was found that it is conspecific with S. vestiens (Valdespino et al. 2015).16.Comments: Selaginella vestiens is characterized by its erect habit, with isophyllous leaves until near the first branch, presence of a stolon and lateral leaves with a cordate base (acroscopically).
In Minas Gerais, S. muscosa could be confused with S. tenuissima but this latter species lacks conspicuous idioblasts on the upper surface of leaves, has lateral leaves with obtuse to rounded apices and, axillary leaves oblong to oblong-obovate.Selaginella producta can be distinguished by usually having a vinaceous color, especially in the field, lateral leaves oblong to ovate-oblong and dorsal leaves with conspicuous idioblasts on the upper surface.Among the species that occur in Minas Gerais, S. flexuosa is differentiated by its leaves with a rugose surface, dorsal leaves without idioblasts and green color.The only known specimen (i.e., Lindberg s.n., K) of S. producta in Minas Gerais was cited byBaker (1883: 243), which he included as a syntype of that species.He, apparently, cited the same specimen(Baker 1883: 99)as a syntype of S. lindbergii Baker.Alston XI/1995, A. Salino 2259 (BHCB); Itinga, RPPN Purpureus, 27/VI/2008, T.E.Almeida 1450 (BHCB); Pedra Azul, 19/X/1988, R.M. Harley et al. 25212 (SPF); Idem, 28/V/1999, A. Salino et al. 4728 (BHCB).