A rewarding partnership

Together, the two organisms are far better equipped to cope with life than either partner by itself. Lichens can exists in extreme conditions where no other plants are found. Their choice of habitat reflects their differing needs for moisture. Most lichens will not, however, growhappily in industrial towns and cities. Their highly sensitive mechanism for absorption of water vapour and other gases cannot bear the extreme dryness and pollution of such areas. Yet some forms are adapted to foul air.

So close is the relationship between a lichen8217;s fungus and alga that they reproduce little blisters that contain tissues of both partners; the blisters readily break away from the main body and the tissues gradually develop into the lichen. The fungus and alga work in unison so successfully that a lichen can live for hundreds, or even thousands, of years.