Hi Gang, A discussion on another list (cacti) prompted me to look up the definition of a phylum, or merely a taxon. I found the following wording and realized it is almost precisely what I learned in college in my plant taxonomy class. One key part of the definition is the word "arbitrary." Definition: "A phylum is part of the hierarchy of classification of organisms. It is an arbitrary grouping; that is, it is developed from a combination of scientific observation, theorizing, and guesswork in an attempt to find order in the complexity of living and extinct life forms. The same is true of all classification levels above and below it except for species, which consist of organisms known to be capable, at least potentially, of interbreeding" (FROM: "Phylum," Microsoft® Encarta® Online Encyclopedia 2000; http://encarta.msn.com/ © 1997-2000 Microsoft Corporation. All rights reserved.) It occurred to me that much miscommunication (or misunderstanding) might derive from the arbitrariness of taxonomic decisions. Such decisions as where to place a division (e.g., these plants belong to 2 different genera) are inherently tricky when there is no universal definition of "how far apart organisms must be in order to belong to different genera." The decisions are not silly, or taken without great deliberation, but they do involve some educated guesswork and hypothesis-testing and hence, have an arbitrary element. It is no wonder that people disagree about where to draw the boundaries. The boundaries are placed according to human decisions, but there is no higher authority that controls "where" to place a boundary. Human-created rules (such as the ICBN) have no inherent mechanism to force anyone to agree with anyone else about where to place a split, or where to lump. In 2003 the Angiospermy Phylogeny Group (AGP II report) lumped several monocot families "back" into the Alliaceae and the Asparagaceae. If this arrangement catches on, such families as the Agapanthaceae and others will be footnotes in history. The decision is arbitrary but well-thought-out and the rationale for such lumping is contained within the article (see pages 403 and 404 for the discussion). I've put the article online so interested parties can read it. It was published in the Botanical Journal of the Linnean Society, 2003, 141:399-436. LINK: Angiosperm Phylogeny Group II Report, 2003 http://www.opuntiads.com/pdf/APG%20II_2003.pdf Cordially, Joe Conroe, TX