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Pictorial supplement to The Fifth Kingdom - Chapter 7

Lichens -  Dual Organisms

(24 pictures)



Exposed rock faces on the north shore of Lake Superior, Northern Ontario, almost entirely covered by lichens.



Landscape near Schefferville, northern Quebec. The spruce trees are there courtesy of their ectomycorrhizal fungal partners, and the ground cover is entirely composed of lichens.



crustose lichens on tree bark - road to Dingo Beach, Queensland, Australia.



Verrucaria zone on rocks along shore at   Letite, New Brunswick, Canada (also seen along west coast)



a basidiolichen with Omphalina (Tricholomataceae) as the mycobiont, the green alga Coccomyxa as phycobiont.   The association is sometimes called Botrydina (courtesy of Fred Notzel).
   X 1.5



model of a lichen thallus, showing round algal cells among fungal hyphae.



vertical section through lichen thallus: algal cells are stained dark blue.



foliose and crustose lichens on rock, Highwood Pass, Alberta, Canada
   X 1/3



Cladonia rangiferina ("reindeer moss") (Cladoniaceae, Lecanorales), with sterile, branched podetia
   X 1



a Cladonia sp. showing basal squamules, erect podetia and apical brown apothecial ascomata
   X 1



Pilophorus aciculare (Stereocaulaceae,   Lecanorales) - podetia on a stone
   X 2/3




colonies of Umbilicaria (Umbilicariaceae, Lecanorales): the large black dots are apothecial ascomata
   X 2/3

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Icmadophila ericetorum (Leotiales) on rotten stump, with convex, pink apothecial ascomata.
   X 1



discolichens on tree bark   The orange (left) and brown disks (right) are apothecial ascomata
   X 2/3



the discolichen Letharia vulpina on a small conifer branch
   X 1.



vertical section through half of an apothecial ascoma of Physcia (Physciaceae, Lecanorales).   Algal cells (pale green with dark centre) are present in the margin and underside of the ascoma.
   X 20



a pyrenolichen, Pyrenula nitida (Pyrenulaceae, Pyrenulales) in tree bark.
   X 1/2



tips of archaeasceous asci



soredia - cells of a green alga caged by fungal hyphae.



steps in lichen synthesis (SEM)



a lichen-encrusted tombstone, the kind of thing that inspired lichen-dating



distribution of fruiting (solid red dots) and sterile (red outlines) lichens in Montreal. Small red dots indicate absence of the lichens.



sulphur dioxide levels in Montreal. Higher values correlate strongly with the occurrence of sterile lichen thalli, or absence of lichens (see above).
Lichens are thus seen to be sensitive indicators of air pollution.



Ascoma of Mycosphaerella ascophylli embedded in the thallus of the brown seaweed, Ascophyllum nodosum. The fungus is always present, and may indicate a kind of reversed lichenization - or a universally distributed parasite.
   X 100


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