Mitthyridium luteum

Mitthyridium luteum

Range Map

The clade is common in western Pacific islands and sparsely distributed in Peninsular Malaysia and Borneo

Description

Lineage: Mitthyridium luteum

Latin name: Mitthyridium luteum (Mitt.) Robinson
Synonyms:
Thyridium luteum Mitt.
Syrrhopodon papuanus Broth.
Mitthyridium papuanum (Broth.) Robinson
Syrrhopodon glaucinus Besch.

General description:
Plants robust usually yellow-green in color. Branches variable, but occasionally up to 4 cm long. Leaves 3.5-4.5 mm long, 1.0-1.5 mm wide, linear, straight and closely inserted along the stem. The lamina is triangular-lanceolate with margins occasionally sub-involute. Stereome (border of hyaline cells) nearly reaching apex and often serrate along the leaf from just above the cancellinae to the apex. Costa percurrent or ending just below the apex. Laminal cells small (5-7 mm wide). Cancellinae typically occupying 1/5 leaf length and composed of 20 cell columns. Sporophytes occasional with seta length never exceeding 1 cm.

Diagnostic phylogenetic characters: [move the cursor over the image to view the morphological matrix]
The characters that differentiate this lineage from its closest relatives, subluteum, perundulatum, and jungquilianum are few. Still its distinctness as a unique monophyletic group is reasonably sufficient to warrant a name. This group has a smoother appearance than its relatives, owed to its few to no papillae. Also this group has more extensive serrations along its leaf margin than its closest relatives.

General phylogenetic characteristics of the "luteum complex":
All of the groups in this linear leaf "luteum complex" (subluteum, jungquilianum, luteum, and perundulatum) except perundulatum have small cancellinae that occupy no more than 1/5-1/7 the total leaf length. All have state 1 for the shape of the transition from cancellinae to lamina. All except luteum have extensive serrations along the leaf margin. All have very few border cell columns (approximately 7 or less). All except perundulatum have a border that does not widen into the stereome characteristic of Mitthyridium until the very base of the leaf (state 5 or 6). All except perundulatum have an acute lead apex.

Diagnostic phylogenetic characters (synapomorphies and/or autapomorphies) were assessed by optimizing via ACCTRAN morphological characters to the 80 taxon total evidence phylogeny decribed in the Phylomonography&Mitthyridium section bulleted above.

Gemmae frequently present.
Gemmae are rough, having visible projections (see gemma figure in glossary).
Gemmipars absent
Cancellinae – on average 20 cell columns on each side of the midrib.
Cancellinae composed on average 1/5 the total leaf length.
Transition shape between lamina and cancellinae /\.
Small or no marginal serrrations present.
Margin serrations cover the majority of the leaf (except at the cancellinae) where present.
The length of the margin taper (from 4 to 2 cells wide) composes 2/3 of the total leaf length.
Hyaline border (stereome)– no wider than 7 marginal border cell columns.
Margin more or less flat and unstratose.
Leaf apex acute.
Leaf tip rhizoids rarely present.
Leaf base rhizoids rarely present.
Leaf not significantly undulate.
Papillae infrequent or absent.
Papillae do not obscure the cell outlines in transverse sectional view.
None or 1 papillae per laminal cell.
Papillae not present on the adaxial side of the costa.
Adaxial epidermis present.
Abaxial epidermis weak or not present.
Adaxial stereid band present.
Abaxial stereid band present.
Costa shape generally elliptical.
Morphological autapomorphies (diagnostic characters): 3, 4, 10, 12, 13, 16, 17 and 18.