Day 41: East meets West for today's essay! A friend recently sent me two lichen specimens from Maine in the hopes that I could identify them for her. One of them was a member of the generic category of "Old Man's Beard lichens," specifically Usnea filipendula (Fishbone Beard, top photos). It put me in mind of my favourite among the Usneas, Methuselah's Beard (U. longissima, lower photos), so I thought it would be fun to present them paired, and thus took a short hike to a location where longissima is abundant.
As you can see, Fishbone is much more compact and delicate. Longissima grows in graceful strands up to ten feet in length. Filipendula branches abundantly, and Methuselah's Beard consists of threads on a central stem, much like a Christmas garland. A microscopic view reveals that isidia (grain-like reproductive units which detach easily from the thallus) are present on both specimens, but are more numerous in the case of filipendula. Both species are excellent air-quality indicators. Sensitive to even small amounts of pollution, Usneas only grow where the air is pure.
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