Tricholoma dryophilum  Murrill

As the name suggests ("Oak Loving"), this is one of the most common Tricholomas under Live Oak.

Stipitipellis and caulocystidia
Tricholoma dryophilum  under Eucalyptus globulus

Tricholoma dryophilum is jumping hosts to the relative new comer in California -- Eucalyptus globulus. Several collections were examined carefully to explore the possibility whether they represent Tricholoma eucalypticum, a native Australian Tricholoma associated with Eucalyptus. The findings confirmed that these are Tricholoma dryophilum.