to claim them. In most lichens, it is the fungus that builds the structural tissues of the thallus (body), as well as the characteristic fungal fruiting structures. Its predominance is such that we often speak loosely of a "species of lichen, "when we mean more precisely a species of lichen fungus; the lichen algae, of course, have their own separate scientific names. The lichen-forming fungi represent nearly one-fifth of all known species of fungi (Hawksworth et al. 1995), yet they are rarely given adequate attention in mycology. It seems their behavior is too different from that of other fungi for many mycologists to feel comfortable with them. Nor is their place in botany secure. Although lichens, as photosynthetic living things, fit within the broad biological concept of "plant, "this term has been increasingly co-opted for use in a narrower, phylogenetic context that excludes all but green algae and their embryophyte ("land