Dear Miroslav and others,
I have a sneaking suspicion that 'Sorrow' and "Tina" have common parentage because Triffid Park have plants growing in their nursery labelled as "Sarracenia purpurea Tina, from Gent" (the from Gent bit is not on their website). This assumption is based on the "Gent" from their label meaning the Beligan Ghent where the cv. 'Sorrow' is apparantly from. My plants were brought direct from Triffid Park at their open day last year and the label is the original from their nursery, so I place some weight on its intent.
Of course, one would need to ask Trifid Park to be 100% sure.
It is also worth noting that the current Meadowview Research Station Sarracenia catalogue has a Sarracenia "Horizon" (p. 21) on offer with similar markings to cv. 'Sorrow'. It was apparantly bred by Dave Evans as a hybrid between Sarracenia flava and S. rosea (or S. purpurea var. burkii, depending on whose taxonomy you subscribe to).
The Meadowview catalogue is available online at: http://www.pitcherplant.org./Meadowcatalog2010.pdf (warning - 5 MB file). For ease of download, I suggest going to www.pitcherplant.org and saving the catalogue from there (link at top of page).
John, Canberra, Australia.