For 10 points, name these organisms that are symbiotic combinations of a fungus and an alga.
These organisms were previously placed in the phylum mycophycophyta (MY-ko-FY-co-FY-tuh), and they are typically classified by growth forms such as "crustose," "filamentous," and "fruticose." They can subsist in extreme environments, but their extreme susceptibility to pollution makes them useful gauges of air quality and ozone depletion. One of them known as R. tinctoria (ARR tink-TOR-ee-uh) is boiled to yield the pH indicator litmus. For 10 points, name these organisms that are symbiotic combinations of a fungus and an alga.
These organisms were previously placed in the phylum mycophycophyta (MY-ko-FY-co-FY-tuh), and they are typically classified by growth forms such as "crustose," "filamentous," and "fruticose.
{lichens}