Sui generis
In local government, a "sui generis" entity is one that does not fit with the general scheme of local governance of a country. For example in England, the City of London and the Isles of Scilly are the two "sui generis" localities, as their forms of local government are both (for historical or geographical reasons) very different from those of elsewhere in the country. 
In a press conference during which reporters were trying to analyse his political personality, Huey Long said, "...say that I am "sui generus", and let it go at that."
Senecio eboracensis
The science of this plant is that it is a hybrid species whose parents are the self-incompatible and promiscuous Sicilian "Senecio squalidus" (also known as Oxford ragwort) and the self-compatible and tenacious "Senecio vulgaris" (also known as Common groundsel). Like "S. vulgaris", "S. eboracensis" is self-compatible, however, it shows little or no natural crossing with its parent species, and is therefore reproductively isolated, indicating that strong breed barriers exist between this new hybrid and its parents.
It is thought to have resulted from a backcrossing of the F1 hybrid of its parents to "S. vulgaris". "S. vulgaris" is native to Britain, while "S. squalidus" was introduced from Sicily in the early 18th century; therefore, "S. eboracensis" has speciated from those two species within the last 300 years.