This guide is an attempt to consolidate all information concerning the biology of the Echinosteliales, including uniform species descriptions for all of the species, and to make this available to interested persons in an open access journal. The Echinosteliales are a small group of myxomycetes with relatively minute sporangia and a unique plasmodial trophic stage (a protoplasmodium). These protoplasmodia, which are a defining characteristic of the order, are relatively small (20-150 mu m in diameter) amoeboid stages with sluggish protoplasmic streaming and plasmodial movement which, as far as it is known, do not form a reticulum or undergo fusion with other plasmodia, but do undergo binary plasmotomy after reaching an upper size limit with each plasmodium produces a single sporangium. The minute sporangia produce a relatively limited number of spores and, except for one stalk-less species, they have a distinctive stalk consisting of a fibrillose tube having amorphous material in the lower region and closing at the upper end to produce a solid region. This morphology, along with developmental and DNA studies indicate that this order is probably the evolutionary basal group of the dark-spored myxomycetes.
