368 RIK A RD STERNER 



countered in shady moist broad-leaved forests (Swed. ■»lunddalder>^), such as 

 Glyceria lithuanica Lindm. (= G. remota Fr., Poa lithuanica Gorski) and Cinna 

 pendula Trin. 



Ptdmonaria obscura exhibits a different distribution (Plate ii). Owing to its 

 limit of distribution towards the north-west in Central Sweden, it agrees with the 

 distribution of many of the previously mentioned continental species. It should 

 be observed that Pulmonaria is lacking in Norway. 



Anemone ranunciiloides has a similar distribution in South Sweden. Neverthe- 

 less it is more southerly and rarer in Central Sweden than Pulmonaria. In Scan- 

 dinavia as a whole, Anemone has quite a different distribution from Pulmonaria. 

 It is widely distributed in Norway, and also occurs sparingly in Jamtland and 

 Medelpad (see too Appendix I, p. 408). 



Ranunculus cassubicus shows a peculiar distribution of another kind (Plate 15). 

 P'rom its abundant distribution on the other side of the Baltic, the species has 



o 



immigrated, evidently from Finland and Aland, to the east of Central Sweden, 

 chiefly to Uppland. But it is difficult to explain the extremely peculiar 

 occurrence of the species in one or two neighbouring localities in the north of Sma- 

 land. There are several continental species which have probably reached Swe- 

 den from the east by the same route (some such species have been mentioned 

 above on p. 360; cf. plate 12). Almost without exception, however, these species 

 have attained a much more extensive distribution in Central Sweden: in most 

 cases, in fact, they have occurrences so far to the west as the south-east of 

 Norway. One of the reasons why Ranunculus cassubicus forms an exception in 

 this respect is perhaps to be sought in the fact that it easily forms hybrids 

 with Ranunculus auricomus. These hybrids are fertile, it is true, but as the 

 latter species is so much more abundantly represented in the localities and their 

 surroundings, the result must be that Ranunculus cassubicus disappears sooner or 

 later (cf. Sterner 192 1 b, p. 132). In accordance with this circumstance, there 

 occur in Uppland, Vastmanland and the south-cast of Ualarne, outside the distri- 

 bution-area proper of Ranunculus cassubicus, a number of occurrences of transi- 

 tional forms to Ranunculus auricomus. In fact, that is the state of things along 

 the whole of the western limit of Ranunculus cassubicus in east-central Europe. 



Some species are distributed in Scandinavia only to the south of the South 

 Swedish highland: Corydalis cava, Thalictruin aquilegiifolium, Ulmus foliacea 

 Gilib., and Ulmus laevis Pallas. Of these species Thalictrum and Ulmus laevis go 

 very much more to the north in Russia, while Ulmus foliacea, on the other hand, 

 is more southerly there. 



The continental »grove» species of South Sweden form quite an insignificant 

 part of the abundant species of the »grove» flora. With one or two exceptions 

 the species are distributed either over large parts of South Sweden or only in 



