Rhizocarpon disporum (Naeg. ex Hepp) Müll. Arg.

Single-spored map lichen, map lichen

About plant names...

This is one of several "map lichens," so-called because at (very) close range, each tiny lichen is bordered by black spores that resemble borders on a map.

Identification: This is a crustose lichen, meaning that it forms a very thin layer, in this case over rock. It is pale gray or brownish gray, looking a bit like paint that dried too fast and cracked. If fruiting bodies (apothecia) are present (for example, in photo 6), they appear as small black dots less than a millimeter in diameter.

Online References:

Stephen Sharnoff Photography

CalPhotos

References:

Walewski, Joe, Lichens of the North Woods, Kollath+Stensaas Publishing, 2007, p. 67

1 · 9/19/2009 · Acadia National Park, Bar Harbor, Maine · ≈ 5 × 3½″ (13 × 9.2 cm) ID is uncertain

2 · 9/19/2009 · Acadia National Park, Bar Harbor, Maine · ≈ 17 × 12″ (44 × 29 cm) ID is uncertain

Rhizocarpon disporum description by Thomas H. Kent, last updated 25 May 2020.

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3 · 9/19/2009 · Acadia National Park, Bar Harbor, Maine · ≈ 8 × 5″ (19 × 13 cm) ID is uncertain

4 · 9/19/2009 · Acadia National Park, Bar Harbor, Maine · ≈ 8 × 5″ (19 × 13 cm) ID is uncertain

5 · 9/19/2009 · Acadia National Park, Bar Harbor, Maine · ≈ 9 × 6″ (23 × 15 cm) ID is uncertain

6 · 4/3/2010 · Mt. Battie, Camden, Maine · ≈ 5 × 3½″ (13 × 9.2 cm)

7 · 9/29/2013 · North Bubble Hike, Acadia National Park, Bar Harbor, Maine · ≈ 9 × 6″ (22 × 15 cm)

8 · 9/15/2016 · Cadillac Mountain Summit, Acadia, Bar Harbor, Maine