The Urban Pantheist

The edges of the thallus of this fungus suggest hammered metal, or at least they did back when such things were common, and lichen common names were up for grabs. Anyway, this is called "hammered shield lichen," Parmelia sulcata*


Most of the visible part of it, and the part that we call Parmelia sulcata, is a fungus. The color comes from a green alga called Trebouxia, which is safely cared for within the flesh of the fungus, protected from drying out and blowing away. Or perhaps it is a prisoner, prohibited from living a free life apart from it's symbiont (there are free-living Trebouxia out there, apart from the lichen symbiosis).


The fungus depends entirely on the algae living inside it, to photosynthesize and make food for both organisms.


* Little shield with grooves

Much of the most beautiful and fascinating wildlife on Antigua is at the beach. This is a tiny mollusk with mother-of-pearl and a spot of copper blue.

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Terrestrial algae growing on the front of a golf cart. I don't know even how to begin trying to identify this organism more specifically, but these people seem to be working on it. I suspect I'd need a microscope and a whole lot more book learnin'. Also, I think I have a crush on the phrase "aero-terrestrial algae." ("Part of the aero-plankton.")

I told you there were more pictures. Remember the fresh travertine terraces I showed you a week ago? Well, after several hundred thousand years of them building up and whatnot, they turn into this pile of rock behind my dad here. Actually, that rock is probably in the millions of years old, and came from a nearby mountain. Seismic activity shoved it over and into a new little mountain formation, which they call "The Hoo Doos."

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Photos by cottonmanifesto. Location: On an Ailanthus tree in front of the Brookline Water and Sewer division.

Urban species #320: Green shield lichen Flavoparmelia caperata

Lichen is a life form that grows in some of the least hospitable habitats on earth. It grows in the Sahara desert and on the rocks of Antarctica. Yet it is fairly rare in the city. Even though lichen can survive extreme temperatures, long droughts, and even saline conditions, it suffers in the presence of air pollution. Lichen growth, or the absence of it, is used as an indicator of air quality. Not surprisingly, lichen populations are on the decline worldwide. New England, directly downwind of the electricity generating coal plants in the midwest, shows lichen decline even in rural areas.

Lichens are a distinct form of life, composed of two unrelated organisms in intimate association. A fungus forms the main body, or "thallus" of the lichen, which has imprisoned within it a photosynthesizing partner. The partner is either a green alga or a cyanobacterium: a single-celled creature that makes food out of sunlight. The fungus derives nourishment from the efforts of the photosynthesizer, which in turn is protected from drying out by the body of the fungus. They grow together as a single being, spreading very slowly over many decades. When it is time to reproduce, the fungus produces spores that contain cells from both the fungus and the alga. In some species the spores contain only fungal spores, and they must encounter the proper algal partner on a substrate in order to properly develop. Lichens are pioneer organisms, growing where others can not. Some species grow on bare rock, helping to break it down, a step in the creation of soil. Species that grow on tree bark do not harm the tree.

Green shield lichen is an unusually pollution-tolerant species. Because of this it is one of the most common lichens in urban areas, growing on the bark of trees. Ecologically equivalent lichens include species that are bluish, or bright orange. Distinguishing similar lichen species from one another requires chemical testing.


Several different lichen species, including F. caperata, crowd for space on this tree's bark.