Melpomene pilosissima (M.Martens & Galeotti) A.R.Sm. & R.C.Moran

  • Authority

    Lehnert, Marcus. 2013. Grammitid ferns (Polypodiaceae). II. . Fl. Neotrop. Monogr. 112: 1--121. (Published by NYBG Press)

  • Family

    Polypodiaceae

  • Scientific Name

    Melpomene pilosissima (M.Martens & Galeotti) A.R.Sm. & R.C.Moran

  • Description

    Species Description - Plants epiphytic or epilithic, rarely terrestrial. Rhizomes very short, ascending to erect, 0.8-1.2 mm diam. Fronds to 22.5 cm long, patent to stiffly pendent, inserted onto the rhizomes at acute angles, closely arranged (internodes 0.5-3.0 mm), caespitose. Rhizome scales to 5.5 x 0.6 mm, (8—)10—12(—16) cells wide across bases, clathrate, dark brown to brown, strongly iridescent, lanceate, narrowly cordate at bases, acute to attenuate at tips; apical cells 1-8, linearly to furcately arranged. Petioles 26-80(-100) mm long, 0.5-0.8 mm thick, terete to weakly marginate from the lowest segments, with many, long, dark brown to castaneous, setiform/ciliform hairs 0.8-3.0 mm long, simple and branched clavate hairs of crosiers and young fronds sometimes persistent on older fronds. Laminae to 125 x 8-22 mm (ca. 2/3 of frond length), firm-herbaceous to chartaceous, usually matte, narrowly elliptic to lanceate (broadest at and/or below the middle), round to broadly cuneate at bases, short-acute at tips. Rachises dark brown to black, planar and slightly sunken adaxially, hemispherically protruding abaxially, sparsely to densely hairy abaxially and in the proximal half adaxially. Largest segments 5.0-12.0 x 1.0-2.6 mm (4-5 times longer than broad), segments weakly ascending (60-80°), inequilateral at bases, fully adnate, long-deltate to oblong, the tips obtuse to acute; midveins not visible to partially visible abaxially; 1-3 proximal segment pairs markedly smaller than the following segments, sometimes remote, but not auriculiform; hairs few to many, evenly distributed on the abaxial laminae, always some along the margins, at least one at the tips; hairs not clustered in sori, hydathodes well developed, conspicuous. Sori 1-6 pairs per segment, with setiform hairs 1.5-2.0 mm long scattered in and around them.

  • Discussion

    Melpomene pilosissima and its allies often are confused. Morphologically, the paraphyletic Melpomene pilosissima group (Lehnert et al., 2009a) can be characterized by short rhizomes that are usually erect to decumbent, rarely shortly horizontally creeping, with the fronds caespitose (less than 5 mm apart); lanceate to narrowly lanceate rhizome scales with thick, dark brown, cell walls; and long to very long, usually dark brown to castaneous, setiform hairs. All species of Melpomene with setiform/ciliform hairs regularly present on margins and adaxial laminar surfaces and/or having only few or no hydathodes belong to this group. It includes two morphologically distinguishable subgroups, one consisting of M. michaelis, M. jimenezii, M. vernicosa, and M. xiphopteroides with hairs clustered in the sori, and the other of M. huancabambensis and M. pilosissima without hairs clustered in the sori.

    Within its range, Melpomene pilosissima is most similar to the epiphytic M. xiphopteroides: scale width, number of apical cells on the rhizome scales, and pubescence show the same variability in both species. Melpomene xiphopteroides differs mainly in the patent to weakly ascending segments with obtuse to round tips (vs. segments weakly ascending with obtuse to short-acute tips in M. pilosissima), laminae that are broadest at or above their center with the bases long-decurrent to truncate (vs. laminae broadest at and/or below the middle with round to broadly cuneate bases), and petioles that are usually marginate to alate from the proximal segments, wings sometimes thin and ephemeral (vs. terete or rarely single petioles marginate). Furthermore, M. xiphopteroides may have darkened (dark brown or reddish) stomata, which do not occur in M. pilosissima as defined here. On average, the laminar hairs of M. pilosissima are longer than those of M. xiphopteroides (mean length 1.5-2.0 mm vs. 0.8-1.5 mm in M. xiphopteroides), but they may measure 1.2-2.0 mm in both species.

    One of the two varieties of Melpomene xiphopteroides distinguished here, var. acrodontia, predominantly has fronds with truncate bases, which superficially look like those of M. pilosissima. However, it occurs only outside the known range of this species. See M. xiphopteroides var. acrodontia for further discussion.

    Melpomene pilosissima often is confused with M. personata, which is easily distinguished by the longer, creeping, horizontal rhizomes with diffusely arranged fronds and the hairs clustered in the sori (vs. rhizomes erect to ascending, laminar hairs evenly distributed abaxially in M. pilosissima). Both show a considerable variation in the visibility of the midveins and the abundance of hairs, but M. pilosissima on average is hairier than M. personata, whereas the midveins are often better visible in the latter species. Plants of M. pilosissima with visible midveins are more frequent in the south of its range. Some stout individuals of such plants were described as a separate species, M. tsatchelae Labiak, but it is here regarded as a variety of M. pilosissima.

    The species is named for the very abundant, pilose pubescence of the plant.

  • Distribution

    Mexico, Guatemala, Honduras, Costa Rica, Colombia, Venezuela, Ecuador, and northern Peru, in cloud forests at 2000-3500(-3850).

    Mexico North America| Guatemala Central America| Honduras Central America| Costa Rica South America| Colombia South America| Venezuela South America| Ecuador South America| Peru South America|