Old limestone fence –a haven for lichens and mosses.
Griggs Reservoir, Columbus Ohio.

Flanking the west bank of the Scioto River in Columbus, Ohio, USA, there is a small park with a French-sounding name (Duranceau Park). The woodland remnants there are strongly influenced by the limestone bedrock and outcrops. Local limestone was quite some time ago used to construct a pretty little fence that marks the boundary of the park, separating it from the backyards of the adjoining residential properties.

Limestone wall is a haven for mosses and lichens.

Limestone wall is a haven for mosses and lichens.

The wall is a haven for mosses and lichens. One of them is a crustose lichen that is almost indistinguishable as to whether it actually is a lichen, rather than, say, a fossil or a mineral deposit. This is pitted stone lichen, Bagliettoa calciseda. (Earlier manuals referred to this as Verrucaria calcidseda.) The body if this lichen (its  “thallus”) is within the stone (endolithic). The reproductive spore-bearing portion of this lichen –tiny flask shaped “perithecia” –are sunken into depressions in the limestone. Pitted stone lichen is widely distributed in northern and temperate regions wherever there is limestone.

Bagliettoa calciseda

Bagliettoa calciseda is a pitted white crust on limestone.

Several of the other crustose lichens produce their spores in a more typical, obvious, and evident manner: a disk-shaped structure called an “apothecium.” Often the apothecia are all, or almost all, that can be seen of the lichen, as the thallus is thin and inconspicuous, or even endolithic. Some of the most colorful lichen apothecia are orange ones in the genus Caloplaca.” This beauty is “sidewalk firedot lichen,” Caloplaca feracissima.

Caloplaca feracissima is "sidewalk firedot lichen."

Caloplaca feracissima is “sidewalk firedot lichen.”

An especially charming, although more subdued, lichen that also exists mainly as apothecia is one I like to call “buckeye lichen.” This is Sarcogyne regularis, the real common name of which is “frosted grain spored lichen.”:

Sarcogyne regularis looks like tiny buckeyes.

Sarcogyne regularis looks like tiny buckeyes.

“Sterile” crustose lichens, by which we do not mean germ-free, but rather lacking any spore-producing structures (i.e., apothecia or perithecia), are among the most challenging to identify. But here’s an easy one. It’s mealy firedot lichen, Caloplaca citrina. The thallus consists mostly of granular yellow-orange soredia (powdery granules consisting of algal cells and fungal hyphae, capable of dispersing and then developing into new lichens as a means of asexual reproduction).

Caloplaca citrina is mealy firedot lichen.

Caloplaca citrina is mealy firedot lichen.

OK, I know what you’re thinking…that picture shows a bunch of apothecia…what kind of sterile lichen has apothecia? Aha! You spied a different lichen…those gray and white disks are “mortar-rim lichen,” Lecanora dispersa. This species, quite the calciphile, is common even in cities, as the calcium in the concrete upon which it grows buffers the the effects of acidic air pollution.

Here’s another picture of Lecanora dispersa, at the edge of a fossil brachiopod.

Lecanora dispersa and brachiopod fossil.

Lecanora dispersa and brachiopod fossil.

The wall is home to some foliose lichens as well.

Limestone wall is a haven for mosses and lichens.

Limestone wall is a haven for mosses and lichens.

One of them is a strikingly white(ish) one called “frost lichen,” Physconia detersa.

Physconia detersa

Physconia detersa is “frost lichen.”

Frost lichen is called that because the lobes are largely coated with a whitish “pruinia,” powdery frost-like deposits of some combination of crystals of pigment, crystals of calcium oxalate, and dead cortical cells. The photo below shows the frosty nature of the Physconia lobes, as well as some pretty severe competition with a colorful other foliose lichen, Xanthomendoza ulophylloides.

Physconia and Xanthomendoza

Physconia and Xanthomendoza.

There are several similar genera of medium-sized foliose lichens distinguished, in part, by color. Phaeophysica is brown, with a black undersurface. The species shown here, I believe, is “powder-tipped shadow lichen,” Phaeophyscia adiastola.

Phaeophyscia adiastola lichen

Phaeophyscia adiastola is a shadow lichen.

Hey, what about the mosses? They’re there. (Aren’t I reassuring?) Cord glaze moss, Entodon seductrix is a shiny carpet moss (pleurocarp) with fingerlike branches.

Entodon seductrix is "cord glaze moss."

Entodon seductrix is “cord glaze moss.”

A moss that was at first tricky to identify because it looked so twisted when dry I thought it was tornado moss (Tortella) turned out, under close examination, instead to be bear claw moss, Barbula unguiculata.

Barbula unguiculata is "bear claw moss."

Barbula unguiculata is “bear claw moss.”

Barbula leaf tips have a claw-like projecting tip.

Barbula unguiculata leaves

Barbula unguiculata leaves