Drosera rotundifolia Round-leaved Sundew CC DDD N
This isn't rare but it does grow in bogs and swamps usually where the sphagnum moss is dominant. It is an insectivorous plant which is a shy flowerer. Small flies are caught in the glue tipped sticky hairs on the leaves and digested to supplement the nitrogen poor habitat. It can tolerate quite acid conditions and I have seen it flourishing in bogs of measured acidity less than pH 3. (pH is a measure of the acidity and is roughly defined as minus log to the base 10 of the hyroxonium ion activity - but you knew that). The difficulty isn't locating this plant, it's getting close enough to it without stepping up to your waist in the black smelly mud of its usual habitat.
You can cultivate Drosera in tissue culture (an agar medium) and it likes it even better than bogs on rain soaked acid moorland.
D. rotundifolia needs acidic bogs so is absent from much of the chalky and limy areas of central and southern England but is found all over Wales, Scotland and Ireland.