Investigation of Phaeocollybia in British Columbia,
Washington, Oregon and California has led to a better understanding of
the
characters and biology of the genus as a whole. Generically significant
characters
– pseudorhizas, pellicular veil, tibiiform diverticula,
and sarcodimitic tissues – are examined in depth with four variations
of branched and unbranched pseudorhizal patterns outlined.
Basidiome development is traced from subterranean initiation to fully
mature emergent basidiomes. Hypotheses on the ontogeny of
Phaeocollybia basidiomes and biological associations are developed
based on extensive observations of primordia and numerous field
excavations. Comparisons between rhizomorphs and the thread-like pseudorhizal
extensions of certain species are made and the term
‘rhizomorphic pseudorhiza’ is introduced. Possible biological
strategies are explored and evidence for consideration of Phaeocollybia
as a mycorrhizal genus is presented.