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Ab~ra~Isozyme markers were used to investigate the origin of the polyploid liverwort, Pellia borealis (gametophytic n -18), which was believed to represent an autopolyploid form of Pellia epiphylla (n -9). Enzyme variation was studied in four taxa: polyploid P. borealis, two recently discovered sibling species of P. epiphylla complex, and the closely related P. neesiana (n -9). (3ametophytes of the polyploid showed a complex electrophoretic phenotype for three diagnostic enzymes (DIAl, MPI1 and ACO) in contrast to simple pattern in all haploid taxa. It was postulated that the pattern found in the polyploid represents a 'fixed heterozygons' phenotype resulting from aUopolyploidy. Alleles present in the polyploid were found (with only one exception) in the two sibling species of the P epiphylla complex, suggesting that they are the parents of the allopolyploid. Pellia neesiana was excluded as a donor of either of the genomes. Variation in the polyploid suggests at least three separate origins of P. borealis.

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Intra- and interpopulational polymorphism in the production of phenolic compounds is described in Polish populations of <em>Pinus sylvestris</em> L. Two mutually exclusive forms of pine trees are present in changing proportions in all populations studied. This allows three groups of populations to be distinguished. The character of this differentiation is discussed.