Several of the live oak trees in the older part of St. John’s Cemetery in San Mateo have branches on which grow bluish-gray foliose lichens with ruffled edges lined with black cilia. The thallus appears to be attached to the substrate mostly in the middle, leaving the edges curling up. On some, small round soralia could be seen (a soralium is where a lichen produces soredia, which are small bits of fungal hyphae and phtyobiont that can be released to produce a new lichen).
After consulting Stephen Sharnoff, A Field Guide to California Lichens (Yal Univ., 2014), I’d place these lichens in the genus Parmotrema; without doing any chemical tests, I’d guess P. arnoldii Powdered Ruffle Lichen, or P. perlatum Common Powder Ruffle.
Living in a cemetery gives me the opportunity to observe a nice diversity of lichens. I went out this evening to see some of this diversity; my camera served in stead of a hand lens.
This crustose lichen, covering an area about the size of a quarter, was growing on a marble gravestone. The magnification of the photo shows how the lichen has etched an indentation into the stone. To make an accurate identification of crustose lichens, I’d need both a microscope and far more knowledge than I currently have. But this may be in the genus Caloplaca: “The 25 to 30 species [of Caloplaca] reported from California … occur very widely on trees and mostly calcareous rocks. Caloplaca saxicola is common and one of the first crustose lichens collected by beginners” (Mason E. Hale Jr. and Mariette Cole, Lichens of California [Berkeley: Univ. of Calif. Press, 1988], p. 190).
The foliose lichen above, about an inch across, and found on a piece of granite, may be in the genus Xanthoparmelia. According to Hale and Cole, “Xanthoparmelia is by far the dominant foliose lichen on granites, schists, shale, and other non-calcareous rocks throughout California…. Two species, X. cumberlandia and X. mexicana, are common and collected almost everywhere in the state.”
If I were to get serious about identifying lichens, I’d need to go out and get the K, C, and P reagents, an inexpensive USB microscope, and a few other things. Then I’d have to get serious about studying them: dissecting them, looking at them under the microscope, etc. Is it enough to just look at lichens without identifying them? or do I want to engage in more serious study of them? Heraclitus advised that “those who are lovers of wisdom must be inquirers into many things indeed” (DK35); but how deeply should one inquire into each of those many things? One only has so much time in this world; a serious in-depth study of one topic means less time to inquire into the many other things.
These lichens were growing on reddish soil exposed by a road cut, in the redwood forest above Camp Meeker, California. The lichens in both photos are approximately the same size; in the first photo, the edge of a nickel appears at lower left to provide a sense of scale.
As to identification, these lichens are in the genus Cladonia: the primary thallus consists of whitish-green squamules (the little leaf-like things at the bottom of the organism); and arising from the squamules is the podetium, an upright structure characteristic of the genus Cladonia. But to determine which species of Cladonia, I would have had to collect some samples and carefully examined them. In Lichens of California, Mason E. Hale Jr. and Mariette Cole state that “Cladonia is one of the first lichens collected by amateurs; since I am a rank amateur when it comes to lichens, it is thus no surprise that I paid so much attention to these showy and fascinating lichens.