I haven't ever heard Laurie speculate as to the origins or potential meaning to the daisy wheel symbol outside what he has been able to demonstrate in terms of it's use as a design aid in specific buildings which he has documented thoroughly. See his articles in TF #70 and #90. Laurie is not a symboligist. Ken, are you familiar with these articles. He has also writted an in-depth study of the geometry of the Barley Barn at Cressing Temple which was given to the students at last years course as part of the study materials.

I've also never heard him speculate as to it's demise, but my thoughts would be that some of the forces at play included: standardization of measurement; the role of the architect becoming separate from the builder and it's subsequient quick development as a separate trade with separate skills/methods, etc.; technology such as improved and readily available rules, graduated squares, tapes, drafting tables, etc; the advent of numbers based systems for manufacturing and building (e.g. the square rule); the publication and widespread use of carpenters manuals and pattern books (beginning in the 18th century) replacing the system of local/regionally specific,inherited knowledge and methods with more or less "standard" practices and standard patterns -- these are just a few off the top of my head.