De dotterbloem in Nederland

515 specimens of the polymorphic species Caltha palustris from 55 Dutch localities were studied morphologically and cytologically. Two cytotypes could be distinguished, a cytotype with 32 chromosomes and another with 56 chromosomes. These two cytotypes have slight morphological differences and different ecological preferences which although incompatible in crosses are insufficient for distinguishing separate species or even subspecies. The studies lead us to the conclusion that Caltha palustris is a species with large genecological differentiation in its populations. The intraspecific polyploidy, which could have arisen by mutations, will have enhanced the polymorphism of the species, resulting in series of more or less discontinuous ecotypes with associated morphological characteristics. Some populations of Caltha were rooting at the nodes of their stems, a manner of vegetative propagation; they are treated as a variety of Caltha palustris: C. palustris L. var. radicans (Forst.) Beck.