Acrocordia gemmata
Most lichenized fungi are in the Ascomycota phylum, which are distinguished by their microscopic, internal, sac-like reproductive structures in which spores are formed (according to Wikipedia, "asco" comes from the Greek for "wineskin"). This is different from Basidiomycota, the "typical" mushroom-forming fungi which have spores that bud out of microscopic, external, club-shaped structures (according to Wikipedia, "basidio" comes from the Greek for "base" or "pedestal"). Sometimes people mistakenly assume that the visible reproductive structure, the ascocarp or apothecia, of ascomycete fungi is the sac-like structure we are talking about, leading to confusion when they see a structure that doesn't really look sac-like at all! Like in the case of A. gemmata, which forms little volcano-like perithecia. But get in closer, as in these microscopic cross sections of the perithecia, and you can see the "sacs" we are referring to!
See those little tubey-wormy things? Those are the sacs!
And those little pill-shaped guys? Those are the fungal spores! They will get ejected from the perithecia and will have to find an algal partner to associate with to grow into a new lichen! Thanks for joining me on this very brief crash-course is mycology.
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