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The following points highlight the two main thallophytes found in lichens. The thallophytes are: 1. Parmelia (Foliose Ascolichen) 2. Dictyonema (= Cora) (Basidiolichen).
Thallophytes # 1. Parmelia (Foliose Ascolichen):
Thallus Morphology:
Thallus is leaf-like, and attached to the substratum by a small portion of the thallus. Characteristic cup-shaped ascocarps (i.e., apothecia) are scattered on the mature central part of the thallus.
Thallus Anatomy:
A cross-section of the thallus shows internal differentiation of 4 zones-uppermost compact hyphal layer, i.e., upper cortex; then algal layer which possesses algal cells intermingled with loose hyphal zones; compactly arranged hyphal medulla zone and lastly the lower cortical hyphal zone with rhizomes.
Reproductive Structure:
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Apothecium:
It shares the characters of the parent thallus in colour and consistency. It is typically cup or disc-shaped. In T.S. it shows a hymenial layer with asci and paraphyses lining the inner surface of the cup.
Ascus:
It is club-shaped and slender with 8 ascospores.
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Ascospore:
It is bi-celled, elliptical and light coloured (Fig 4.1).
Identification:
Presence of symbiotic thallus association (i.e., an algae and a fungus forming the thallus).
CLASS: LICHENS
Fungal component belongs to ascomycetes and ascocarp formed as reproductive structure.
SUB CLASS: ASCOLICHENS
Fruit-body apothecial type.
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SERIES: GYMNOCARPEAE
Fruit-body apothecial type, apothecia cup-shaped with hymenial layer lining the inner face of the cup.
ORDER: LECANORALES
Hymenial layer with asci and paraphyses lining the inner surface of the cup.
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FAMILY: PARMELIACEAE
Ascospores bi-celled, elliptical and light-coloured, ascus 2-8 spored.
GENUS: PARMELIA
Thallophytes # 2. Dictyonema (= Cora) (Basidiolichen):
Thallus Morphology:
Thallus is membranous and adheres to the stem bark with conspicuous bracket-shaped basidiocarp as fruit-body.
Thallus Anatomy:
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The thallus has centrally located algal layer surrounded on both sides by compactly arranged fungal hyphae.
Reproductive Structure:
Basidiocarp:
It is like those of bracket fungi. A T.S. through basidiocarp shows the following layers – upper hyphal layer, algal layer, medulla zone and lower fertile hyphal zone with basidium and basidiospores.
Basidium:
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It is tubular and sterigmatic (4 in number) and intermingled with paraphyses.
Basidi-spore – It is small and ovoid in shape (Fig 4.2).
Identification:
Presence of symbiotic thallus association (i.e., algal and fungal association).
CLASS: LICHENS
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Fungal component belongs to Basidiomycetes and produces basidiocarp.
SUB CLASS: BASIDIOLICHENS
Fruit body gymnocarpous, hymenium unilateral or amphigenous; sterigmata relatively small.
ORDER: APHYLLOPHORALES
Fruit body typically cobwebby, membranous, leathery, hymenophore warty, spores globose to ellipsoidal.
FAMILY: THELEPHORACEAE
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Thallus membranous and adheres to the stem bark with conspicuous bracket-shaped basidiocarp as fruit body.
GENUS: DICTYONEMA (=CORA)
