The Science of Botanical Art

Lichens 

By Dick Rauh

Originally appeared in The Botanical Artist, Volume 12, Issue 4

 

In a recent exhibition that I curated, entitled Ferns, Lycophytes, Fungi and Lichens, I was amazed by the appeal of the latter group. We received plenty of fern entries, nary a club moss, some fungi, but a surprising number of lichen paintings. Not being very cognizant of the subject I was forced to call on experts in the field to verify the accuracy and nomenclature of the portrayed species. (Notice, however, that ignorance doesn’t inhibit me from writing this piece!) I was delighted when none of the scientists called upon threw any of the pieces out, but to the contrary asked the prices of a number for possible purchase. It seems we are getting better and better at depicting the natural world, in all its diversity. 

Recent work has clarified some of the questions earlier experts asked. Where do we place this intriguing group? How mutualistic is the symbiosis involved? What is the latest taxonomic thinking? 

First, let’s tackle those points which seem consistent. Lichens are an association of two distinct organisms, fungi and photosynthetic bacteria. The old story has the cyanobacteria or blue-green algae supplying nutrients and sometimes fixing nitrogen for the fungus. What is not so clear is what the fungus does for the algae. Do we have parasitism here? However you slice it, the special association creates a group of about 25,000 species of a particular morphology unlike any other fungi. The existence of the food making body within the fungal body has allowed lichens to inhabit some of the most hostile areas on earth. They exist from the bare surfaces of desert rocks to the frozen substrate of polar regions and there are a few that are completely aquatic. 

These extremely slow-growing organisms appear ubiquitous, except that they are very sensitive to pollutants and in some area are becoming rare (what’s happening to us in those places?). Rocks, undisturbed soil, fence posts, tree bark and branches are colonized by various species (lichens have even been found growing on the backs of large forest beetles). Because where they grow is so relevant to species identification I believe it behooves us to include the substrate in our paintings instead of isolating the subject against our usual white background. For the botanical purists among us perhaps we can let the substrate fade into white. The body of a lichen takes three forms that are of interest to us as artists. They may be organized into flattened, scale or leaf-like structures with overlapping edges that grow horizontally and these we call foliose. These are attached to the substrate by means of root-like threads called rhizinae. Crustose lichens usually lack any lobes and cling tenaciously to rocks by the whole of their lower surface. The surface of crustaceous lichens is often divided into tiny, frequently more or less hexagonal areas. These are the ones that you can’t take back to the studio unless you bring along the rock. Third are the branching, pipe-like forms called fruticose. Here the thallus is erect and bush-like or pendant and tassel-like. It is attached only at the base. 

I recently hiked a newly opened trail in Acadia National Park in Maine and was brought to a dead stop by a stand of gray-white fruticose lichens, maybe 6 inches high at most that were probably reindeer moss. They stretched for yards in a spruce woods and appeared a miniature ghost forest that took my breath away 

Lichen taxonomy, like so many branches of botany, has undergone shifts in genera in recent years due to our growing knowledge of molecular data. Because of this I suggest a check for identification is best handled on the Internet. I have a piece I identified as Parmliais now firmly in the genus Hypogymnia, so what do I do with the old calligraphy that is part of the painting? At this point perhaps we should do all our identification in pencil. It’s exciting to see how new discoveries are still being made, but somewhat frustrating to realize that some of the most recent texts are out-dated even as they are published. 

I believe one of the appeals of this group is the subtlety of their colors and the almost infinite variety of their surface textures. I have seen some vivid orange and yellow mostly crustose lichens. The majority that appeal to our more reticent painterly hearts fall into the range between white, pale green, blue-greens, tan and brown. It appears that sexual reproduction of lichens, because of their associative nature is a complicated process, and generally they tend to use asexual ends. Fragmentation of the thallus, or specialized asexual propagules called soredia (usually powdery white masses) or isidia that appear like small cylindrical to flattened outgrowths on the upper surface of the thallus do the job. Fruiting bodies (similar to most fungi) do occur however. They are called ascocarps that contain the asci (sacs) that hold the spores. The red tips on the ascending branches of British Soldiers are examples, as are the cup-like or disc-like structures on many other genera. 

Although a lichen can extend over an area that makes a one-to-one rendering meaningful (chances are you are painting a specimen hundreds of years old because of their exceedingly slow growth rate) some of the most intriguing aspects of lichen structure are best revealed in enlarged work. The exquisite lichen drawings of Lucy Catherine Taylor come to mind. For me, used to the symmetry inherent in flower morphology, the almost rampant irregularity of the groups’ structure has a special appeal. Within the vast range of lichens I have yet to come upon any surfaces that were predictable, or exactly duplicated any other. I think it is perhaps this challenge, more than any other, that draws us to these amazing organisms. Or perhaps it is the sentimental wonder in this contentious world of ours, that there are actually two disparate living things that get along in mutual harmony. _

 

References: 

How to Know The Lichens, Mason E. Hale 

The Observer’s Book of^ Lichens, K.A. Kershaw & K.L. Alvin 

Morphology of Plants and Fungi Bold, Alexopoulos & Delevoryas.

  • Parmela, watercolor, ©Dick Rauh 2002