>How different does a plant have to be to be designated as a new form/species?
Good question. There are approximately 10 different (well, the
meta-taxonomists still debate if the 11th attempt is really different...)
attempts at answering this, but unfortunately it seems neither of which can
avoid some tautology ("two species are different from each other if -and
only if- they are different species").
>For instance, I can see obvious similarities between P. "Pico de Orizaba" and
>other P. moranensis forms (the flower shape and markings for instance) yet
>this plant has a glabrous scape whereas P. moranensis doesn't (from what
>I've seen). Is there a kind of point score system?
No.
>I have a plant labelled as P. caudata which has P. moranensis
>characteristics. There is a reference in Jan's list which lists it as
>being P. macrophylla.
The reference you mean is P.caudata sensu HEMSLEY (non SCHLECHT.). This was
a single misconception in the literature. It has nothing to do with the
P.caudata in the horticultural trade (P.caudata SCHLECHT.), which is
considered conspecific with _P.moranensis_. _P.macrophylla_ is a completely
different plant ("summer" leaves with distinct petioles marginally with
long hairs!), and very rare in cultivation (easy to kill).
>From what I remember from Slack's first book, P. caudata has a large rosette
>of leaves. My plant on the other hand is only a few inches across at most
>with *very* pronounced leaf-edge rolls and has somewhat rosy pink flowers.
Are the corolla lobes cuneate?
>Is my plant likely to be a P. moranensis var. caudata, P. macrophylla or is
>it totally mislabelled?
It is probably a member of sect.Orcheosanthus (the "enfant terrible" in the
genus).
>I've just picked up a new Ping hybrid - P. (morrii x ehlersae) x grandiflora.
>I can't find any mention of a P. morrii in my literature - is this another
>Mexican Ping?
I have never seen this name before. Where did you pick it up?
> This plant has the most leaves I've ever seen on a Ping. (I
>count about 30 visible live leaves, including "buds" at the moment!)
These come from _P.ehlersiae_.
Kind regards
Jan