STUDIES IN RANUNCULUS SUBGENUS BATRACHIUM (DC.) A. GRAY. Ill

An account is given of Ranunculus hederaceus and R. omiophyl/us including information on distribution, ecology, floral biology, hybridization, variation and karyotype analysis. Formal descriptions with full synonymies and typifications are also included. Both species are morphologically and ecologically very similar and can exist as diploids or tetraploids. They are largely sympatric throughout their geographical ranges and, occasionally, grow intermingled. They show complete hybrid inviability at the diploid level and hybrid sterility at the tetraploid level but at the same time can be regarded as belonging to a single potential common gene-pool (hologamodeme) as they form fertile hybrids with R. tripartitus and R. baudotii. In spite of a high degree of inbreeding and numerous isolated populations no genotypic differen-tiation has been detected in either R. hederaceus or R. omiophyl/us