Thanks, everyone, for the wealth of information. I'm learning a lot from this thread. Now, to further confuse things, what does this name mean: Paphiopedilum wardii 'Longford' CC/OSCOV ? It looks like a species but why is there another name after the lower-case name? :hmm

Minda, that is a Paph. wardii that received a CC Award (Cultivation Certificate, if I recall it correctly!) from the OSCOV (Orchid Society Council Of Victoria).. The name 'Longford' is the clonal name given to that particular plant, and together with the certificate CC/OSCOV should be carried in the future for that plant and all divisions taken from it... As well, in case the plant is mericloned (not very common for slippers!), the mericlones should as well carry the same name (exception, when the mericlone is mutated to an extrem that it clearly differentiates from the original plant)

clonal names are given to identify individual plants. Not awarded plants can have clonal names, but awarded plants must have a clonal name, in order to ensure which is the particular plant receiving the award.

Thanks, Ramón. Is it still a species?

A species is still a species, even if it has a clonal name. The clonal name only serves to differenciate a an individual within a species for having outstanding or unique characteristics. Hybrids can also have clonal names.

Andrew,
Thsnk you for your comment about invasive. That finally made sense. As an old farm boy I considered many plants invasive (Poison Ivy for example) and they are native.