Studies of fertility of Dicranum majus in two populations with contrasted sporophyte production

Some populations of the dioicous moss Dicranum majus Sm. in southern Norway do not or only rarely produce sporophytes, while most populations in centr al Norway produce sporophytes frequently. Two populations of D. majus in sp ruce forest, one from southern Norway (without sporophytes) and one from ce ntral Norway (with many sporophytes) were investigated to find differences in sexual reproduction between them. The population in southern Norway had only a few perichaetia and neither dwarf males nor sporophytes, while peric haetia, males and sporophytes were abundant in the population from central Norway. Shoots with dwarf males formed perichaetia more often than shoots w ithout males, and the proportion of fertilized archegonia increased with in creasing numbers of males on the shoots. Genetic differences or some earlier environmental 'disaster' related to ext reme drought or heavy pollution loads are discussed as possible explanation s for the sparse sporophyte production in southern Norway. In order for spo rophytes to be produced in the population in southern Norway, new males mus t be established from spores from outside.