Steve, Jim McK., Jane, and all, I also encountered the term Rassenkreis first in regard to Lepidoptera, but specifically to the butterfly Junonia coenia, which also ranges from Florida across the central USA to Mexico and Central America. It its case, I think there is at best very limited fertility between the Florida and the Central American forms, but with the same continuous fertility between neighboring populations. Steve described the situation very well indeed. I'm pretty fluent in German, but I also had to check the spelling before proceeding with my original posting. I thank Jim McK. for reassuring me that cline is also applicable. "Cline" might be more botanical, or it might be just a matter of years. I encountered "Rassenkreis" at least 40 years ago. It could easily have fallen by the wayside in that length of time, especially considering the degree of Anglicization of science in the intervening years. Jane, I have not encountered "continuum" used in a biological sense before. This probably shows how narrow my biology reading has been over the years. Whether Jim's Lilium greyii/canadense situation is a cline or a localized intergradation between two young, mostly allopatric and closely related species is perhaps debatable. I certainly don't know the situation with Lilium. Where you have two mutually interfertile species existing in sympatric populations, if there is a barrier, they can be pretty stable. Introducing the human element may be all that is needed to overcome such a barrier to interbreeding. I can see where, over time, and intermediate population could take over or it could be extinguished. If the parent species include individuals that are not fertile with members of the other species, they might prosper as the hybrids decrease. Getting back to vernacular names, I'd say there are many things you simply cannot discuss using vernacular names. On the other hand, the day is not far off when species, local populations, and individuals will be identified and defined by their DNA. It's just the direction things are going and will continue to go, barring some Armageddon or other broad catastrophe. Best wishes, Jim Shields in central Indiana (USA) ************************************************* Jim Shields USDA Zone 5 Shields Gardens, Ltd. P.O. Box 92 WWW: http://www.shieldsgardens.com/ Westfield, Indiana 46074, USA Tel. ++1-317-867-3344 or toll-free 1-866-449-3344 in USA