Fascinating Lichens of Sri Lanka

Sclerophyton
Arthoniales Roccellaceae
15
Sclerophyton is a genus confined to the tropical and oceanic areas of the world.
But it is possible that this genus is found in all parts of the world below an altitude
of 1500m, with a mean temperature over 5° C and an annual precipitation over
500mm. In Sclerophyton, the highest species diversity occurs in South and Central
America and tropical Asia. Temperate Europe, Central America, Australia and
Southeast Asia have their own species. Out of all known species of Sclerophyton,
only four are considered as widespread.
Typically, corticolous species of this genus are found on palm beaches, coastal
scrublands and in woodlands. Saxicolous species grow on shaded, often
overhanging rocks. Some species grow in tropical rainforests. Most species are
distributed within a small area. All species of Sclerophyton grow on nutrient poor
to nutrient rich, acid to neutral or inert substrates, such as smooth, acidic bark,
hard wood and sclerophyll leaves (hard leaves with short internodes).
Ramalinaceae
Fr
VC
Ramalina usnea
Description The fruticose thallus is corticolous, pendulous, long, yellowish
brown, and branched with ribbon-like branches that are spirally twisted, and are
often cracked. Pseudocyphellae are linear. Soralia are absent. Medulla is solid.
Apothecia are not found in Sri Lankan specimens.
Status Very common species.
Habitat Mostly restricted to humid high elevation forest above 1400 m.
Locations Horton Plains and Nuwara Eliya.
Though this genus is mostly found in dry habitats, the species included here is
observed in an upper montane area above 1300 m, along the Pattipola road in
the Nuwara Eliya District. This is the first species of this genus to be recorded
in Sri Lanka (Weerakoon & Aptroot unpublished). It is possible that many other
species of this genus could be present in Sri Lanka, as other genera of the family
Roccellaceae are frequently recorded.
Apothecia round to elongate or asteroid, immersed, generally in groups or lines,
disc exposed, pink or pale to dark brown to black, often pruinose, margins white
to grey, often fusing to form stromata (a thick compact wad of hyphae, often
covering or supporting a group of ascomata); Asci: 8-spored; Spores: colourless,
clavate, septate (3-10) or muriform.
Chemistry Thallus UV- or UV+ yellow , PD+ yellow or PD+ orange , K+ Yellow or
K+ yellow turning red, C+ red.
Roccellaceae
Oceanic areas: Pertaining to a climate characterized by mild, wet winters, cool,
moist summers, and frequent fogs.
146 Fascinating Lichens of Sri Lanka
Fascinating Lichens of Sri Lanka 147