It basically indicates that someone does not yet know how to correctly write plant names. There may have, at one time, been an option to use an X, to simply indicate that a plant was of hybrid origins, that has not been a valid option with horticultural names, for at least several decades.
In botany, sometimes plants are named and published, then it is later discovered that they are naturally occurring wild hybrids. When that happens, an "X" is inserted after the Genus name and before the specific epithet, to indicate that the plant is of hybrid origins.
This may still be correct for some botanical names, but not horticultural - though don't quote me on that, as I am not a botanist. Though the
ICBN (International Code of Botanical Nomenclature) is available online, last I looked, (this is the Vienna version, from the 17th congress) and it was searchable. Apparently it is now updated by the
ICN or (International Code of Nomenclature) and is a PDF, which I linked to the acronym
ICN, which is a documentation of the changes to the Vienna code, making it now the Melborne code, after the 18th congress, held there.
This usually happens when someone confuses botanical nomenclature with horticultural nomenclature, they work together, are similar, yet not the same.
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Generally, botanists discover new plants, study them, photograph, measure, draw them, describe and publish them. Collect specimens, smash them flat, dry them out, and file their dead remains in herbaria.
Horticulturists, may do many of the earlier listed things that botanists do, but usually avoid the later things, those that come after, "Collect specimens,".