332 RIKARD STERNER 



about Christiania and in various places in Denmark, especially north-eastern Jutland 

 and north-eastern Zealand. These isolated occurrences are worth special atten- 

 tion. They would nowadays generally seem to be interpreted as relics of an 

 ancient, more continuous distribution area. With regard to certain occurrences 

 in Jutland that belong to these species. Warming has, among others made himself 

 spokesman of a similar opinion (1904, p. 78). 



In the neighbourhood of Christiania the following steppe species have isolated 

 occurrences: Asperula tinctoria at Ostenso (Plate 17), Phleum Boehmeri: in many 

 localities (Plate 5), Pulsatilla pratensis (Fig. 19), Seseli libanotis (p. 334), Tri- 

 folium montanum (p. 301), and Allium montanum (Plate 6). 



In north-eastern Jutland there are, inter alia: Asperula tinctoria (formerly at 

 Aalborg), Crepis praemorsa, Eryngium campestre, Medicago falcata. Prunella 

 grandiflora (Plate 6), Senecio integrifolius (Plate 6), and Trifolium alpestre (Plate 

 6), to which may be added Anthericum liliago (Central European distribution). 

 On Zealand there are somewhat isolated occurrences of Potentilla arenaria, Pul- 

 monaria angustifolia, Prunella grandiflora, and Thesium ebracteatum. 



The occurrences in question correspond to very favourable ecological condi- 

 tions in the isolated localities. The soil is strongly calcareous, and the tem- 

 perature-conditions in the neighbourhood of Christiania differ greatly in favour of 

 xerothermous species. Hence it is not so remarkable that these steppe species 

 are able to thrive in the localities, but the strong isolation makes the occur- 

 rences peculiar. 



Concerning many steppe species with a comparatively wide distribution in 

 Southern Scandinavia a division of the distribution area into two branches, an 

 easterly and a westerly one, forms one of the chief features. The eastern branch 

 comprises Sweden to the east (and north) of the South Swedish highland; the 

 western one is formed by occurrences in Skane, on the Danish Islands, Jutland 

 and, if you like, in the neighbourhood of Christiania, to which may be added 

 for some species one or another locality in South Sweden to the tuest of the 

 South Swedish highland (Plate 6). The distribution branches of some species are 

 sharply defined, as in the cases of Phleum Boehmeri (Plate 5), Crepis praemorsa 

 (P- 315)) 'ii^d Pulsatilla pratensis (F"ig. 19), [cf. also Cynanchum vincetoxicum 

 (Plate 18), Melampyrum nemorosum (Plate 16), Cnidium venosum (Plate 20) etc.]; 

 in other instances the western branch is much weaker, as in the cases of Asperula 

 tinctoria (Plate 15), Trifolium montanum (p. 301), Potentilla arenaria (Plate 6), and 

 Seseli libanotis (p. 334). 



The reason for this division of the South Scandinavian distribution area is 

 naturally in the first place the fact that only the plains on both sides of the 

 South Swedish highland furnish localities suitable for the steppe species; the 

 eastern branch, forming a more continuous piece of land and being poor in precipi- 



