Legitimate but no conclusion yet, per both Tropicos and the GCC.
Centaurea americana Nutt. validly published-1821
http://www.tropicos.org/Name/2...
[Centaurea americana Spreng., Illegitimate-1826
http://www.tropicos.org/Name/1... ]
Plectocephalus americanus (Nutt.) D. Don is validly published--1830
http://www.tropicos.org/Name/5...
Click on the Accepted tab in each of the two legitimately published entries and the other is referenced.
The same is true at the GCC except they note each as a synonym for the other.
Centaurea americana Nutt.
http://compositae.landcarerese...
Plectocephalus americanus (Nutt.) D.Don
http://compositae.landcarerese...
Edit: So a plant floats in limbo and we have no entry for it.
