Here is a classic picture of mycorrhizae. These pictures are high resolution and will look fantastic on computers with modern video cards.
This is the mycorrhizal fungus Laccaria laccata on ponderosa pine. Note the bifuricate shape of the mycorrhizae. You can see the fungal sheath (white area), hyphae, and hyphal strands (if you have 400x vision!).Thank you Jim Trappe for the slide!
This is what the outer fungal sheath of a mycorrhizae actually looks like. As the micrograph shows the hyphae are about 1 micron in width. The bar at the bottom is 10 microns. Note the clamp connections i.e. those raised bulbous looking things! Some of the little dots are (likely) bacteria. Yes, the soil bacteria probably have some interaction with the fungus.
In this photo you are looking at the cross section of a feeder root in mycorrhizal association with a fungus. In the center of the picture you can see the xylem. The large cells are cortical cells. Moving outwards look closely and you will see that the fungus has pushed itself between the cortical cells (Hartig Net: named for Dr. Hartig). Finally, there is the fungal sheath on the outside. The bar in the picture (lower left) is 10 microns.
Come on! Get your face in the screen and look at those cortical cells and the Hartig Net Is this awesome or what? Is this ecto- or the other kind?