Braiding Sweetgrass

promise to provide for the family by hunting. Plant food and animal
food, autotroph and heterotroph—the alga and the fungus also
bring their particular gifts to their union as a lichen.
The algal partner is a collection of single cells, gleaming like
emeralds and bearing the gift of photosynthesis, the precious
alchemy of turning light and air to sugar. The alga is an autotroph,
or one that makes its own food and will be the cook of the family,
the producer. The alga can make all the sugar it needs for energy,
but it’s not very good at finding the minerals it needs. It can only
photosynthesize when it’s moist, but it has no ability to protect itself
from drying.
The fungus partner is the heterotroph, or “other feeder,” since it
can’t make its own food but must subsist on the carbon harvested
by others. The fungus is brilliant at the art of dissolving things and
liberating their minerals for its use, but it can’t make sugar. The
fungal wedding basket would be filled with specialized compounds
like acids and enzymes that digest complex materials into their
simpler components. The body of the fungus, a network of delicate
threads, goes out hunting for minerals and then absorbs those
molecules through its huge surface area. Symbiosis enables the
alga and the fungus to engage in a reciprocal exchange of sugar
and minerals. The resulting organism behaves as if it were a single
entity, with a single name. In a traditional human marriage, the
partners may change their names to or an alga. We name it as if it
were one new being, an interspecies family, as it were: rock tripe,
Umbilicaria americana.
In Umbilicaria, the algal partner is almost always a genus that
would be called Trebouxia if it lived alone or was not “lichenized.”
The fungal partner is always a type of ascomycete but not always
the same species. Depending on how you look at it, the fungi are