PDF - CES (IISc)

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SYSTEMATIC
XXVI. THELOTREMACEAE
A tropical or subtropical family of which the leading characteristic is
the deeply sunk disc of the apothecium :
it has a proper hyphal margin,
and, round that, an overarching thalline margin. The apothecia occur singly,
or they are united in a kind of : pseudostroma in Tremotylium several grow
together, while in Polystroma each new apothecium develops as an outgrowth
from the thalline margin of the one already formed, so that an upright,
branching succession of fruits is built up. It is a very unusual type of lichen
fructification, with one species, P. Ferdinandezii, found in Spain and in
Guiana.
The thallus in all the genera is crustaceous with an amorphous (decom-
posed) cortex; or it is non-corticate. The algal cells are Trentepohlia except
in Phyllophthalmaria, an epiphyllous genus associated with the alga Phycopeltis.
In Polystroma the alga is unknown.
Only one genus is represented in the British Isles.
Apothecia growing singly.
Thallus with Trentepohlia gonidia.
Paraphyses numerous, unbranched, free.
Spores colourless.
Spores elongate, 2- or multi-septate i. *Ocellularia Spreng.
Spores muriform 2. Thelotrema Ach.
Spores brown.
Spores elongate, septate .3. *Phaeotrema Miill.-Arg.
Spores muriform 4. *Leptotrema Mont.
Paraphyses scanty, branched.
Spores muriform, brown 5- *Gyrostomum Fr.
Thallus with Phycopeltis gonidia 6. *Phyllophthalmaria A. Zahlbr.
Apothecia in pseudostromata.
Apothecia united in tubercles 7. *Tremotylium Nyl.
Apothecia united 'by the margins 8. *Polystroma Clem.
XXVII. DlPLOSCHISTA CEA E
Scarcely differing from the preceding family except in the gonidia which
are Protococcaceous algae. The thallus is crustaceous and non-corticate.
The apothecia have a double margin but the outer thalline margin is less
overarching than in Thelotremaceae. The spores in the two genera are
somewhat peculiar: in Conotrema they are exceedingly long and divided
by parallel septa into thirty to forty small cells ; in Diploschistes ( Urceolaria)
they are large, muriform and brown. Conotrema contains two corticolous
species ; Diploschistes about thirty species mostly saxicolous. Both genera
are represented in the British Isles.
Spores elongate, multi-septate, colourless i. Conotrema Tuck.
Spores muriform, brown 2. Diploschistes Norm.
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