When foliose lichens such as the one at the left mature, reproductive "cups" form in the center. These cups, called apothecia (singular apothecium), are provided by the fungal part of the lichen, so it's no accident that they look like the fruiting structure of a sac, or cup, fungus.
At the right is another foliose lichen, this one on a tree twig. The whole picture covers an area about three inches across (8 cm). In this species, the fruiting bodies, instead of being tiny cups, appear at the curled edges of the lichen body.
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