At least, that’s how it looks to me. You be the judge.
It seems pretty clear that crustose and foliose lichens are pretty much two-dimensional. They have length and width, but are, we might say, vertically challenged. Fruticose lichens are beyond all that: they may not even have an up or down. One wonders what they might look like growing in zero gravity!
Fruticose means “shrubby,” and some of these lichens do, in fact, portray shrubs in model railroad layouts or architectural models. Structurally, they vary widely. They may be hollow or solid (as in this Usnea cross-section), but generally have upright forms. Most common here are species of Cladonia, such as “pixie cups,” and Usnea, the beard lichens.Cladonia species are abundant ground lichens in forest areas, forming colonies of graceful pointed or cup-shaped upright structures called podetia. Look closely at the base, where foliose parts of the lichen, the squamules, are often visible. Forms found on soils at lower elevations often go unnoticed because they lack podetia and consist only of squamules. Unlike the Usnea version in the diagram above, Cladonia podetia are hollow. Fruticose lichens may be the ones most apt to be noticed, and then given common names, by the people who share their environments. Where abundant, as in boreal forests and Arctic tundra, they simply can’t be overlooked; this view of Cladina in Maine is a good example. Colorado alpine tundra habitats are similarly lichen-rich, with some of the same species as found in the Arctic, such as “white worms” (Thamnolia vermicularis) and “Iceland moss” (Cetraria islandica).
Genera of Colorado Fruticose Lichens
- Bryoria See Sharnoff gallery, B. fremontii; see also B. fuscescens, B. lanestris, others.
- Cladina 2 (3) species, now placed back in Cladonia See, for example, Reindeer moss; also at Ways of Enlichenment. Very rare.
- Cladonia 36 species, excluding Cladina See Sharnoff gallery of Cladonia and Cladina species
- Dactylina (Allocetraria) madreporiformis See Sharnoff gallery
- Leprocaulon See Sharnoff gallery, L. gracilescens; see also L. microscopicum, L. subalbicans
- Letharia See Sharnoff gallery, Letharia vulpina. Rare.
- Lobaria See Sharnoff gallery, L. scrobiculata; see also L. pulmonaria. Extremely rare! (Technically considered foliose.)
- Ramalina See Sharnoff gallery, Ramalina pollinaria; see also R. obtusata, R. sinensis
- Stereocaulon See Sharnoff gallery, S. tomentosum; see also S. rivulorum, S. glareosum, S. incrustatum
- Thamnolia See Sharnoff gallery, T. vermicularis
- Usnea See Sharnoff gallery; six species here, U. hirta and U. lapponica probably most common