Fascinating Lichens of Sri Lanka

Collema
Jelly lichens, Tarpaper lichens
Peltigerales Collemataceae
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Collema is a large, cosmopolitan foliose genus of blackish grey to very dark olive,
brownish olive lichens which often tend to be gelatinous, pulpy or swollen when
wet. The species become steel grey to dark brownish black when the thallus is
dry. Species of Collema are found on a wide variety of substrates in wet or dry
habitats. The photobiont is a blue green cyanobacterium (usually Nostoc).
Only few species are documented for Sri Lanka as most of the species which
should be placed in the genus Collema are overlooked for Leptogium. Collema
can be distinguished from the related genus Leptogium by the absence of a
cortex. Also, Collema species are never hairy or shiny like Leptogium, which can
have a shiny thallus or white fuzzy hairs. One of the species, Collema coilocarpum,
which belongs to the core group of the genus, is included in this book.
Collemataceae
In Sri Lanka, species of Collema are most abundant at the scrubby edges of high
elevation rainforests. They also occur in the submontane and montane interior
but they tend to be less conspicuous there and are restricted to canopy branches
or to moist shady recesses.
It is worth climbing a tree to reach the canopy branches, to seek out these
treasures in habitats where the species could possibly exist, since they are
stunning black jelly beauties adorned with reddish, orange apothecia. This
genus needs a detailed taxonomic revision in Sri Lanka.
Apothecia lecanorine, developing on the upper surface of the thallus, disc
reddish orange brown; Asci: 4-8-spored, Spores: colourless, 2-to many-celled
(muriform).
Chemistry No lichen substances.
Collema coilocarpum
Description Foliose. The thallus is mainly corticolous, and the upper side is olive
grey, becoming purplish grey blue when dry (latter photos). Isidia are not found,
but often develop erect, thickened lobules or cylindrical outgrowths can be seen
that resemble isidia and can dominate the thallus (as shown in photos). Thallus is
very pulpy and swollen when wet. Apothecia are dense. Discs are orange brown.
The other species which is known to me in Sri Lanka is Collema pulcellum var.
subnigrescens. But the species needs clarification with fresh sampling. It has a
dark blackish olive green upper surface that is deeply ridged. Only seen in one
place at Nuwara Eliya.
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Collemataceae
Status Common, cosmopolitan species. The species is known to Sri Lanka from
early lichen collections and has been documented many times.
Habitat Mainly seen on the mature canopy branches of trees in rainforest edges,
submontane and montane areas.
Locations Central highlands, high elevation wet zone forests, Meemure and
Kalupahana areas of the Knuckles mountain region.
68 Fascinating Lichens of Sri Lanka
Fascinating Lichens of Sri Lanka 69