‘Atragene’ is the collective group name for all the varieties that lay within 4 species ‘families’.
These are
Alpina
Chisanensis
Koreana
Macropetala
They are all early flowering and have nodding flowers (whether single or double) which also attract bees and butterflies - they all have fantastic seed heads after they have finished flowering.
These are also among the toughest clematis in existence as they will thrive in any aspect and any conditions (even coastal areas)