Field Mushrooms Agaricus spp.
This is what most people think of when you say mushroom. They are the typical mushroom shape with a cylindrical stem with a ring and domed cap. The cap colours range from pure white to light brown. Some species have a distinct pattern of brown scales. They have pink or greyish brown gills which become dark brown as the spores mature. The gills are not attached to the stem.
There are two main groups within this genus. Those that stain red and those that stain yellow. The red staining species are all edible and include the field mushroom, the pavement mushroom, the scaly wood mushroom and the cultivated mushroom. They have a sweet earthy mushroom smell.
The yellow staining species again fall into two groups. Those that are permanently stained yellow or orange when bruised and have a sweet aromatic smell similar to almonds or aniseed. They have a round domed cap. These are good edibles and include the horse mushroom, the wood mushroom and the prince.
The other group stain bright yellow and are toxic to some people. The colour appears shortly after handling especially at the base of the stem but eventually disappears. The time this colour change takes depends on humidity. The toxin in these species is phenol which gives them an unpleasant inky smell. The smell appears to be more noticeable to people who are affected by the toxin. The caps of this group are flattened slightly at the top giving them an angular appearance. Species include the yellow stainer and wood yellow stainer.
Agaricus mushrooms can be found in open grassland, hedgerows and woodland and in the case of the pavement mushroom coming up through tarmac. They tend to grow in rings. None of this group grow directly on wood