Mycorrhizae literally means fungal root and describes beneficial relationships between fungal microorganisms and higher plants. Ectomycorrhizae produce hyphae (thread-like nonreproductive filaments) that do not penetrate cortical cell walls (cells between the vascular bundles and the epidermis of plant roots). It is estimated that as many as 4,000 to 6,000 fungal species are involved  in forming associations (mainly in the phyla Basidiomycetes and Ascomycetes) but with relatively few plant taxa. About 10% of plant families have species that form ectomycorrhizae, with the majority being woody plants. The video depicts the mantle (enveloping fungal tissue) that covers the surface of roots.  In addition, ectomycorrhizae often change the shape of the roots (making the roots shorter, broader, or branched), which can be seen in the line drawing depicting dichotomous branching of root tips and the multiple growing points on the roots of white pine (Pinus strobus L.).  A downloadable, high-resolution version of this movie in RealMedia format is available at http://www.agron.iastate.edu/~loynachan/mov/.