Mitthyridium obtustolium

Mitthyridium obtusifolium

Range Map

The obtusifolium clade is one of the most geographically restricted in Mitthyridium. obtusifolium is restricted to the southeastern islands of the Pacfic Ocean. It is often found on coconut palms below 300 m. The clade's closest relative is micro-undulatum, its Indian Ocean counterparts.

Description

Lineage: Mitthyridium obtusifolium

Latin name: Mitthyridium obtusifolium (Lindb.) Robinson
Synonyms:
Syrrhopodon obtusifolius Lindb.
Thyridium obtusifolium (Lindb) Fleisch.
Mitthyridium subfasciculatum (Hampe) Robinson
Mitthyridium samoanum (Schultze-Motel) Robinson
Mitthyridium subobtusifolium (Broth. & Par.) Robinson

General description:
Plants medium-robust and usually yellow-green in color. Branches variable, but occasionally up to 4 cm long. Leaves 3-4 mm long, 1.0 mm wide with spreading shoulders. The lamina is lingulate with a flat or abruptly rounded apex that often can have a small mucro. 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 (as is typical of taxa in Mitthyridium). Laminal cells small (5-7 mm wide). Cancellinae typically occupying 1/5 leaf length and composed of 20 cell columns. Sporophytes rare; seta length ca. 1 cm.

Diagnostic phylogenetic characters: [move the cursor over the image to view the morphological matrix]
Cancellinae/lamina transition (character 3) is almost always flat. Margin serrations +- present and usually extensive. The number of border cells is an average of 12. Margin taper occurs at %25 (from base to apex). Margin apex is flat (micro is acute… a strong difference between the two). Papillae on dorsal side of the costa may be ok for the eastern obtusifolium.

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 present occasionally
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 often flat (or very mildly rounded)
Large marginal serrrations often 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) occurs at 1/4 of the total leaf length (from tip to base)
Hyaline border (stereome) on average 12 marginal border cell columns.
Margin more or less flat and unstratose.
Leaf apex flat.
Leaf tip rhizoids rarely present.
Leaf base rhizoids rarely present.
Leaf not significantly undulate.
Papillae present.
Papillae obscure the cell outlines in transverse sectional view.
Multiple papillae per laminal cell.
Papillae 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): 7 and 11.