Well BaseDrifter and Goodkoalie,
You have helped to uncover a nomenclatural discrepancy. I assume that the IPNI and CP Database, both use the initial publication by Schnell & Determann, in
P: Castanea 62:60 (1997). I do not, presently have access to this publication, so I can't personally verify the information. However, I do have Donald Schnell's 2002 edition of Carnivorous Plants of the United States and Canada, where he does attribute the variety, "montana" to Sarracenia purpurea subspecies venosa, rather than the northern subspecies. If, however, the earlier Castanea publication, does attribute "montana" to the northern subspecies, that would take precedence - even if it were erroneous, at the time.
On a slightly different tack, Sarracenia x readii, though then, or now, not being validly published, was corrected in syntax, since it was named after an L. H. Reade, and there was no valid reason to change the last letter of the Reade name in order to latinize it. It only needed the addition of the final "i". So the misspelling was correctable, especially since, in the interim, no other Sarracenia species or nothospecies was published with the name, S. readei, before the correction was made.
Even invalid publications are important to the history of botanical nomenclature.