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Heimioporus betula (Schwein.) E. Horak

The mature pileus color is actually redder than appears in this image at the left. The taxon appears to be distributed from E USA to Oaxaca, Mexico. Heimioporus alveolatus is a synonym.

The spore ornamentation is manifested generally as circular to semicircular pits that occasionally coalesce. The apex is eroded and is often described erroneously (from light microscope observations) as a 'germ pore.'

betula-sem_spores