Even some plants have a darker, parasitic side. Common cow-wheat (Melampyrum pratense) is semi-parasitic on the roots of a number of plants including blaeberry (Vaccinium myrtillus), while lousewort (Pedicularis sylvatica) and yellow rattle (Rhinanthus minor) are found on grasses. Parasitic plants can increase the diversity of plant species in an area by keeping more dominant species in check.