I was under the impression that praestans was considered
glanduliferum by the RHS. This is unfortunate since,
according to a very close scrutiny of the type by
Dr. Braem, glanduliferum doesn't exist in cultivation.
No other has been found with the correct staminode.
Which means all the 'glanduliferums' in cultivation are
in fact praestans as are the praestans. But then they
are forced to be registered as glanduliferum.