Actually, the "correct" lily is Lilium candidum
, the Madonna lily. It's the ancient lily of the Mediterranean (going back to Minoan art) and is a nearly invariable element in Western images of the Annunciation well down into the middle ages. Usually in it's in a pot, but sometimes it is held as a wand by Gabriel.
Some of the symbolism is obvious. I don't know how it got attached to Easter, though I do know why the Easter lily is a different (Asian) species (L. longiflorum
). L. candidum
is tough as nails as far as climate is concerned (to USDA zone 4) but it is susceptible to viruses. It also isn't as robust as the Easter lily, and perhaps isn't as amenable to forcing. (The Easter lilies in the garden at church are in bloom right now.) The Madonna lily is an odd duck in that it puts out some leaves in the fall, which remain over the winter until the main stem comes up in the late spring. It's a little untidy looking at that point, which may be another reason it isn't as popular.
The business about the Easter
lily growing in Gathsemane is of course complete rubbish. L. longiflorum
comes from Japan and wasn't described in the west until 1794. It would have been completely obvious for the Madonna lily to grow there-- for all we know, it would have been strange if it hadn't grown there. The business about the drops of sweat is something I've never heard; if I had to bet, I'd say it's a Victorian invention.