The concept employed here is generally that of Singer (1986) but with modification and clarification of species characteristics. There has been considerable confusion in distinguishing among these species. The lack of attention by some to the manifestation of the ornamentation at the apex of the spore has contributed to this confusion.
In longicollis and singeri, the apex of the spore is cleaved by the grooves or channels that separate adjacent ribs (costae), whereas elatus and jalapensis possess a shallow circular depression or indentation around which the ribs coalesce. Spore morphology seen with SEM and Light Microscope clearly illustrate this difference.
At present we can distinguish 4 taxa based on spore morphology, presence/absence of a veil, and to a lesser extent, viscidity/glutinosity of basidiome surfaces. However, this number might decrease to 3, if B. jalapensis and B. elatus are considered the same taxon with trans-Pacific distribution.
**REH is grateful to E. Nagasawa (Japan) for material of B. longicollis & B. elatus; B. Ortiz-Santana (Madison, WI) for material of B. singeri, and the herbaria at Field Museum (F) and Guadalajara (IBUG) for loan of specimens from Japan and Mexico.
Key to Species
1. Basidiomata viscid-glutinous and with a veil; costate ornamentation of the spores typically continuous from pole to pole, not united at apex; spore apex traversed by a continuous fissure or fissures --- 2
1. Basidiomata lacking a veil, viscid glutinous or not; costate ornamentation of the spores frequently foreshortened and attenuated, occasionally continuous from pole to pole, united at the apex around a shallow, circular depression --- 3