The morphological variability of two hemiparasitic species, Rhinanthus glaber and Odontites verna, was examined. With the exception of Odontites verna ssp. litoralis and ssp. verna a clinal variation was observed, so that the delimitation of subspecies was found to be difficult. The study of ecological differences is gradually taken up. So the germination of R. minor and R. glaber was investigated. The seed of both species needs a moist chill pretreatment before germination takes place. The seed keeps its viability when stored dry at low temperatures.