Lace Lichen

This “plant” is actually a pairing of convenience of two organisms neither of which is considered a plant in current thinking. It is a kind of lichen which is made up of an alga and a fungus. It is a partnership of convenience because the partners stay together only under conditions that neither could survive alone. When conditions favor one or the other, the favored partner leaves (alga) or expels its partner (the fungus).

Why isn’t it a plant, or more to the point, what is a plant? Based on Classical Greek definition, plants formed a variable group of organisms held together primarily by not being animals. Once the microscope was invented and biologists saw that the living world was far more complex than anyone could have imagined, the old definition became harder to defend. Especially troubling was a group of unicellular and colonial organisms (now in kingdom Protista) that formed a continuous series from definitely animals to definitely plants. This meant that groups in the center possessed a combination of animal and plant characteristics. For example they were green, thus photosynthetic, but they moved and some even captured prey as well.

The really hard organisms to place were those that produced (or captured) chloroplasts when the environment was well lit and relatively poor in nutrients and expelled these same chloroplasts when light was absent and organic food plentiful. That is, they could be “animals” or “plants” depending on the conditions. These organisms were claimed by both botanists and zoologists and thus have two legitimate scientific names.

Yes, I know that you learned in high school biology that every known organism on earth has one and only one correct scientific name. That’s true only if there were only one Nomenclatural Code. But there are two – one for animals and a second for all organisms originally considered plants. The lichen (which is a stable, predictable pair of organisms), has a lichen name. The lichen discussed in this article is lace lichen, Ramalina menziesii. Note that since the partners making up lace lichen can live separately, the partners will have their own names as well.

I was unable to find out the individual scientific names of the partners. However, from the internet, it appears that the algal partner is a green alga (Chlorophyta) and the fungal partner is one the more primitive members of the sac fungi (Ascomycota). This lichen is one of the types that attaches itself to the surface of twigs of living trees and shrubs. So when talking about this lichen we need to mention a third partner. In the Elfin Forest that partner is usually the pygmy form of the coast live oak, Quercus agrifolia, common in the forest.

Lace lichen does best where humidity and coastal on shore winds are highest, so it is particularly abundant along the immediate coast from south-east Alaska to Baja, Mexico. Since lace lichen attaches itself to the outside of a branch or twig, it is what biologists calls an epiphyte. Epiphytes do not harm their host because they are not taking any nutrients from the host. My way of describing the relationship is that an epiphyte is a plant that gets its room from its host, but not its board.

The only way I can perceive of lace lichen being a problem for its usual oak tree host is if it got so massive that its weight caused the twig to break; a very low probability. According to an entry on the internet, lace lichen is actually beneficial to its oak host because it captures air born moistures and nutrients. When the fragile lichen is broken apart, it adds these nutrients to the soil which helps its host. Another internet item noted that small herbivorous animals will not only eat any lace lichen that falls on the ground, but will fight others for the privilege.

Another value that lichens give to their environment is that they utilize sulfur in their photosynthesis. This makes lace lichen, as well as other lichens, important in removing excess sulfur from the air. Lace lichen is also extremely susceptible to air pollution. Therefore it can be used a measure of air quality. Lichen present = good air; lichen absent = bad air. Because lace lichen grows very rapidly, when air pollution is removed, it grows back quickly.

The fungal partner provides most of the actual mass of lichen. Therefore the shape or form lichen takes will be determined by the pattern of growth of the fungal partner. Lichens are considered to have one of three basic growth forms. These are a flat coating of a surface (crustose), a series of flat plates raised from the surface (foliose) or 3-D mass of strings (fruticose). Looking at Bonnie’s drawing assures that lace lichen is a fruticose lichen. Closer examination of the top of her drawing, where the plant would be attached to the twig, shows some wider strands. Attached to these strands are the fungal reproductive structures. In this case, they resemble tiny challis cups. The fungal spores are produced on the upper surface, inside the cup. Note, this is the way the fungus reproduces. The algal partner must figure out how to reproduce on its own. That said, there is a way for the pair to spread together and that is by fragmentation. I suspect that random fragmentation is the most common method by which lichens spread.

When I first came to California, lace lichen was known by another common name. This was “Spanish moss.” However this name is very misleading since it is in no way a moss. It neither resembles any known moss nor is it related to mosses. Even worse, calling this lichen, “Spanish moss”, leads to confusion with the Spanish moss from the South-eastern United States, which is also not a moss. It is flowering plant in the same family as pineapple. The only thing lace lichen has in common with true Spanish moss is its color (gray-green), basic form, and its epiphytic habit.

One last item of which I was reminded while researching lace lichen on the internet is that the California Lichen Society is pushing the California Legislature to designate lace lichen as the state lichen. This would be good for the lichen as well as for its host trees. In the interior of California, one of the commoner hosts is valley oak which is having trouble reproducing due to pressure from agriculture.

by Dirk Walters, illustrations by Bonnie Walters | Dirk and Bonnie Walters are long-time CNPS-SLO members, contributors, and board/committee participants. In addition to his work at Cal Poly, Dirk is the current CNPS-SLO Historian.