Common cow-wheat (Melampyrum pratense) is an interesting flower in that it is a member of the broomrape family and, like other members of the family, it is partially parasitic on other plants. Unlike the broomrapes, however, it does have chlorophyll and so has green leaves and stems and has very delicate yellow tubular flowers.
Whilst primarily a woodland species it is sometimes also found on heaths and in boggy areas; it has a preference for acid soils but does occur elsewhere. Where it occurs in woodland it is usually considered an indicator of ancient woodland. It has a unique association with wood ants who use the seeds to feed their young. In so doing the ants help disperse the seeds but as the ants do not roam far from their nest they spread of the plant is quite slow. Whilst not rare, I would call it uncommon but where it does occur though it tends to be extensive thanks to the work of those ants.
I have not been able to find a clue as to why it is called cow-wheat, its preferred habitat seems hardly to be a place where cows might feed. the Latin name pratense means 'of the meadow' which also seems odd as this is more of a woodland species.