Apelgren, K. 1991. Environmental response of Galium palustre s. lat. in a coastal area in Central Sweden. -Nord. J. Bot. 10: 593-606. Copenhagen. ISSN 0107-055X.Galium palustre s. lat. is a polymorphic taxon. The differences in morphology are correlated with the level of ploidy, but there is also a certain amount of phenotypic plasticity. The plasticity probably contributes to this taxon's successful colonization of a wide variety of habitats. The amount of plasticity was studied for plants from different kinds of habitats in Sweden, both for diploids (G. palustre s. str.) and octoploids (G. elongatum), which were cloned. This cloned material was then transplanted to three different localities in Sweden: a sunny exposed sea-shore, a ditch, and a shady alder swamp. The general pattern of morphology was similar for all material, independent of its origin and level of ploidy, with smaller plants (smaller in several vegetative characters) and a more abundant flowering on the exposed seashore than in the ditch, and the largest plants with a fairly sparse flowering in the alder swamp. The octoploid plants originating from the wooded wetland are the least plastic ones but are very variable within the localities. G. palustre var. balticum shows a similar variation pattern as the others, but there are also genetically fixed differences in some characters between it and G. palustre var. palustre. The changes in morphology of the plants in the different localities occur fairly rapidly (in one month), although the differences are more spectacular one year later.

Morphological variation, chromosome numbers, reproductive system and ecology were studied in Galium palustre s. lat. in some areas in the Baltic land-uplift area. Two cytotypes were found; diploids with 2n = 24 and octoploids with 2n = 96. Each cytotype comprises a large amount of habitat-correlated variation. Despite this, it is fairly easy to destinguish morphologically between the two cytotypes. It is therefore suitable to treat the diploid cytotype as one species, Galium palustre s. str.. and the octoploid cytotype as another species, Galium elongaturn. Both species grow in wet places, such as ditches, lake-shores and wet woodland. There are practically no differences in habitat ecology between them, but a slight tendency can be discerned for octoploids to grow in localities which never dry out, while diploids can grow in drier localities. Only G. palustre s. str. grows on fairly exposed sea-shores. A morphologically distinct from can also be distinguished, including diploids from sea-shores and coastal areas below 5 m. a. s. 1. This ecotype is described as Galium palustre var. balticum var. nov. It is characterised by smooth or nearly smooth stems and short, narrow leaves. It has always a very rich flowering and fruit set, which may be regarded as an adaptation to coastal conditions.