DISCUSSION OF THE AGARICOMYCOTINA

The Agaricomycotina form a large and very diverse group of fungi that are not easy to come to terms with. Yet members of this subphylum include the largest and most conspicuous fungi on earth. If you go for a walk in the woods at any time of the year you will see them. Their diversity has attracted the attention of mycologists for hundreds of years; however it is only in the last ten years, with the accessibility of molecular techniques, that mycologists have come to realize just how rich this diversity actually is. Along with this new appreciation of the great variety within the Agaricomycotina has come the realization that it is very difficult to reconcile what we know to be true based on genetic evidence with what we see. How do you use a system of classification that is not based on physical evidence?

Our approach to classifying the Agaricomycotina begins at the intuitive level, applying concepts in use for more than two centuries. These simple groupings are partly in agreement with modern thought but are greatly simplified. Within each group we then have the opportunity to sort out more natural relationships. Our initial breakdown of the Agaricomycotina recognizes four groups:

• Mushrooms and boletes

• Macrofungi (large fungi) with a familiar mushroom shape. Their basidiomata (fruiting bodies) are soft and do not persist for a long time. Their growth is by expansion or inflation, so they always push obstacles out of their way rather than growing around them; you will not see objects incorporated into their fruiting bodies. Their basidia line the surface of gills in mushrooms and the surface of pores or tubes in the boletes. All have holobasidia.

• Non-gilled macrofungi

• Macrofungi that are not mushrooms and boletes. In some older systems this group will have been assigned to the order Aphyllophorales, now obsolete. The basidiomata are often tough and able to persist for long periods. Many grow by the addition of new hyphae or tissues; when they encounter an obstacle they grow around it and thus incorporate it into their fruiting bodies. Their basidia are produced on a great variety of surfaces including pores and teeth but only rarely on gills. All have holobasidia.

• Jelly fungi

  • Fungi with a conspicuously gelatinous consistency. Many are macrofungi but some are small enough to be called microfungi. Most are able to dry out and then revive, a characteristic that allows them to grow in places that are only occasionally wet. All have cruciate-, tuning-fork- or phragmobasidia.

• Gasteromycetes

• Macrofungi having holobasidia that do not forcibly eject their basidiospores. Because of this all members of the group have specialized means of basidiospore dispersal. Includes puffballs, stinkhorns, birdnest fungi, etc.