Editing Lichen (section)

=== Color ===
[[File:Bipartite and tripartite cyanolichens (10.3897-mycokeys.6.3869) Figure 1.jpg|thumb|Lichens]]
Lichens come in many colors.<ref name=SSFGCL/>{{rp|4}} Coloration is usually determined by the photosynthetic component.<ref name=MSULB>{{cite web|url=https://www.msu.edu/course/bot/423/Plntlist8mosslichen.html|title=Lichens and Bryophytes, Michigan State University, 10-25-99|access-date=10 October 2014|archive-url=https://web.archive.org/web/20111005224410/https://www.msu.edu/course/bot/423/Plntlist8mosslichen.html|archive-date=5 October 2011|url-status=dead}}</ref> Special pigments, such as yellow [[usnic acid]], give lichens a variety of colors, including reds, oranges, yellows, and browns, especially in exposed, dry habitats.<ref name=SJCL>{{cite web|url=http://www.saguaro-juniper.com/i_and_i/lichens/lichens.html|title=Lichens, Saguaro-Juniper Corporation|access-date=10 October 2014|archive-url=https://web.archive.org/web/20150510220114/http://www.saguaro-juniper.com/i_and_i/lichens/lichens.html|archive-date=10 May 2015|url-status=dead}}</ref> In the absence of special pigments, lichens are usually bright green to olive gray when wet, gray or grayish-green to brown when dry.<ref name=SJCL/> This is because moisture causes the surface skin ([[cortex (lichen)|cortex]]) to become more transparent, exposing the green photobiont layer.<ref name=SJCL/> Different colored lichens covering large areas of exposed rock surfaces, or lichens covering or hanging from bark can be a spectacular display when the patches of diverse colors "come to life" or "glow" in brilliant displays following rain.

Different colored lichens may inhabit different adjacent sections of a rock face, depending on the angle of exposure to light.<ref name=SJCL/> Colonies of lichens may be spectacular in appearance, dominating much of the surface of the visual landscape in forests and natural places, such as the [[Lichens of the Sierra Nevada (U.S.)#On rock|vertical "paint"]] covering the vast rock faces of [[Yosemite National Park]].<ref name="LSN">{{Cite journal|last1=McCune|first1=B.|last2=Grenon|first2=J.|last3=Martin|first3=E.|last4=Mutch|first4=L.S.|last5=Martin|first5=E.P.|date=Mar 2007|title=Lichens in relation to management issues in the Sierra Nevada national parks|journal=North American Fungi|volume=2|pages=1–39|doi=10.2509/pnwf.2007.002.003|doi-broken-date=1 November 2024 |doi-access=free}}</ref>

Color is used in identification.<ref name="JJMML">Michigan Lichens, Julie Jones Medlin, B. Jain Publishers, 1996, {{ISBN|0877370397}}, 9780877370390, [https://books.google.com/books?id=-Jo0yP2-69UC&pg=PA8] {{Webarchive|url=https://web.archive.org/web/20161124144607/https://books.google.com/books?id=-Jo0yP2-69UC&pg=PA8|date=24 November 2016}}</ref>{{rp|4}} The color of a lichen changes depending on whether the lichen is wet or dry.<ref name=JJMML/> Color descriptions used for identification are based on the color that shows when the lichen is dry.<ref name=JJMML/> Dry lichens with a cyanobacterium as the photosynthetic partner tend to be dark grey, brown, or black.<ref name=JJMML/>

The underside of the leaf-like lobes of foliose lichens is a different color from the top side ([[dorsiventral]]), often brown or black, sometimes white. A fruticose lichen may have flattened "branches", appearing similar to a foliose lichen, but the underside of a leaf-like structure on a fruticose lichen is the ''same'' color as the top side. The leaf-like lobes of a foliose lichen may branch, giving the appearance of a fruticose lichen, but the underside will be a ''different'' color from the top side.<ref name=ASLTT/>

The sheen on some jelly-like gelatinous lichens is created by [[mucilaginous]] secretions.<ref name=MSULB/>