Parmotrema Lichen

Parmelia praesorediosa

Parmetia praesorediosa Nylander, 1891, p. 18. [For full synonymy see Hale 1965, p. 258.]

TYPE COLLECTION.—Singapore, Almquist (H, Nylander Herbarium 35547; S, isotype).

DESCRIPTION.—Thallus adnate to loosely adnate on bark, 5–10 cm in diameter, light mineral gray to greenish gray; lobes 4–7 mm wide, subrotund; upper surface plane; margins of lobes sorediate (in part sublaminal), soredia powdery in orbicular, linear, or typically crescent-shaped soralia, cilia lacking; lower surface black and sparsely rhizinate at the center, brown and naked in a narrow zone along the margins. Apothecia (not seen in Dominica) rare, 4–10 mm in diameter; spores 7–10× 15–21μ.

CHEMISTRY.—Cortex K+ yellow (atranorin); medulla K– or K+ very faint yellowish, C–, KC–, P– (caperatic acid possibly with protolichesterinic acid intermixed). The G.E.-precipitated crystals are mostly globular.

WORLD DISTRIBUTION AND HABITATS.—Pantropical on palms and hardwoods at lower elevations (sea level to 1,200 m).

This common lichen is usually collected on planted trees, palm, citrus, etc. It is quite variable although easily separated from other sorediate Amphigymnia species by the P– reaction. The thallus and lobes are distinctly smaller than in P. cristifera Taylor or P. dilatata Vainio, two common P+ associates of P. praesorediosa. The relationship to the rock-inhabiting P. mordenii is discussed under that species.

SPECIMENS EXAMINED.—Hale collections: 1 (35682), 2 (35700), and 9 (35389). Roseau Botanical Garden: Evans 50, 51, 60 (US).