Both photos are of the same colony 2 days apart. At least a half-dozen Armillaria colonies were scattered about in the lawn but separated by several meters. No wood was visible on the lawn surface. In each case, however, pushing a spike into the ground at the base of the colony revealed buried wood at depths of ca. 0.3 meters. Several trees in this area were removed in the last 10 years and roots from these trees may have supported Armillaria establishment.
There are several species of reddish Russulas in our area. All seem to have white spores, stout stipes and dry, brittle caps and stipes. Never colonial, they crop up year -round under oaks.
Mushrooms in this genus are short-lived and usually associated with dead trees. Some species release their spores through the liquefaction of the basidiocarp, leaving only a blackish liquid a few days after appearing. However the species pictured here apparently does not do this. Instead the mushrooms gradually decomposed after spores were released from the gills like most mushrooms.
The puffballs (genus Lycoperdon) have a very thin peridium (skin) and release their spores through openings that form, with age, in the top of the puffball. The empty dead remains of the mushroom last much longer than the living stage. This species, in my yard, is always under oaks on bare soil and never in the lawn.
*Arora, David 1986. Mushrooms Demystified. A Comprehensive Guide to the Fleshy
Fungi, 2nd Ed., Ten Speed Press Berkeley Cal.
Below is another pair of unidentified small saprophytic mushrooms growing on a wood substrate. Note the mid-stipe collar, a remnant of the veil which formerly enclosed the young mushroom before its maturation. Although clearly of a different species (and probably a different genus) than the first pair, spores, which were not available, would be required for further identification
Arora, David 1986. Mushrooms Demystified. A Comprehensive Guide to the Fleshy Fungi
Vol. 2 . 10 Speed Press Berkeley California