There were quite a few different daylily species used originally in crosses. Most of those were 'dormant' but a couple were 'evergreen'. The two that Stout originally considered to be evergreen were Hemerocallis aurantiaca and Hemerocallis aurantiaca var 'Major'.
A few years later Stout determined that H. aurantiaca was probably a hybrid and not a valid species. He thought that H. aurantiaca var 'Major' might be a valid species but more information about it from Japan (and more specimens) would be needed. Each was originally collected as only one plant.
Many years later Japanese botanists decided that H. aurantiaca var 'Major' was a valid species and named it Hemerocallis major.
Stout wrote this about semi-evergreen:
"There are wide differences among the large number of hybrid seedlings and named clones in regard to the proportion of leaves that remains green during autumn and winter. Some which have relatively few green leaves in mid-winter may be classed as semi-evergreen or semi-dormant. It is possible that in semi-tropical areas some of these may have a short period of complete dormancy."
Clones means the same as cultivar. Stout grew his daylilies in New York, N.Y.
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About the evolution:
Geneticists basically assume that the dominant form of a gene is the 'normal' form and that the recessive form is the mutation (unless they have other information). In this case that would mean that evergreen is the normal or original and dormant is the newer form. This would fit with the idea that because of ice ages plants survived in the tropics and then later moved North. As they moved North they would have to adapt/evolve to survive the cold winter climates. The assumption would be that dormancy allows a plant to survive cold winters.
