Lichens: Mysterious and Diverse

The science of lichenology, or the study of lichens, has lagged behind other branches of botany, and many aspects of lichen biology are still shrouded with mystery. In fact, the most mysterious aspect of these plants, and the one basic to understanding them, was not known until the relatively late date of 1867: that although outwardly lichens appear to be discrete organisms, they are in fact made up of two very different kinds of plants bound together in a totally unique union. The components of lichens are these: (1) numerous individuals of an alga, usually of a one-celled green type similar to those which commonly give a green cast to the northern or shady sides of tree trunks, but occasionally a filamentous blue-green type like the ones which form the familiar blackish, rank-smelling scum on shallow water, damp soil, or clay flower pots; and (2) strands of a fungus, similar and somewhat related to the bread molds. The arrangement by which they live together as a lichen is referred