Punctelia graminicola
I love learning about a member of a familiar genus I have yet to meet! P. graminicola grows on rocks, moss, and occasionally bark or burned wood at low elevations in North America down in South America. This foliose lichen has a wide, adnate to loosely attached thallus of narrow, sublinear lobes that are pale blue-gray to green-gray on the upper surface, and pale tan on the lower surface. As with other members of the genus, it has point-like or pore-like pseudoceyphellae (openings in the outer layer of the thallus to the inner medullary layer). What's really cool is that scientists actually studied the developmental physiology of these structures within the genus, and found that P. graminicola forms these structures by arranging the medullary hyphae in circular groups and pushing from the inner layer out, shoving the algal layer up, eventually bursting through the cortex, leaving a gaping hole into the lichen!
Ok maybe not "gaping" per se--they are really small. Why does it go through all this effort to form these pores? The prevailing theory is gas exchange for the photobiont layer during photosynthesis, but that likely is only part of the story, as not all lichens have pseudoceyphellae but all perform photosynthesis.
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info: source | source
