Seasonal variation in Melampyrum nemorosum

Variation of Melampyrum nemorosum was studied. Eleven morphological characters usually described as seasonal and considered to be significant for infraspecific division of the species were measured. It was found that some of the characters change markedly during the flowering period in the same population. The number of internodes has been believed to be the most important character, although it is one of the most variable. The present study does not support the traditional distinction of three seasonal taxa in M. nemorosum, as only two population groups could have been distinguished. The early-flowering populations occur in meadows and flower in May and in the first half of June. The late-flowering populations occur predominantly in forests and shrubs and flower from the beginning of June until September. These two groups differ primarily in the total number and length of internodes. Differences in the number of branches and that of flowering branches are frequent but less constant across different biotopes. No differences in the number of intercalary internodes between the both populations groups were found. Seasonal types of M. nemorosum can be taxonomically treated at the level of variety. The variety nemorosum should be reserved for late populations of the species. The epitype of the name of this variety is established, because the lectotype of M. nemorosum is a fragmentary plant which is impossible to determine with certainty. For nomenclatural reasons, the early populations are described in the present papers as a new var. praecox.