292 RIKARD STERNER 



shore, where there are next to no mosses and lichens, but the flora nearly coin- 

 cides with that of the grass heaths. 



Certain steppe species in South Sweden belong neither to dry meadows nor 

 to grass heaths. Concerning the mode of occurrence of these species the following 

 brief observations may be made: — 



Carex ligerica, Holosteum umbellatum, Peucedanum oreoselinum, Poa bulbosa, 

 and Ranunculus illyricus occur chiefly in localities, where, thanks to human inter- 

 vention, the vegetation is sparse and more or less like a colony vegetation, such 

 as fallow fields on sand, roadsides, earth roofs etc. According to Areschoug (1889), 

 Peucedanum occurs in its distribution area in Skane on »dry, gravelly pasture- 

 lands*. The natural occurrence of these species in southernmost Sweden, especi- 

 ally on Oland, is on steep southerly slopes or rocky pavement with a thin vegeta- 

 tion. The phanerogamous flora of these localities closely resembles that of certain 

 grass heaths (see further Sterner 192 1). 



Silene viscosa, a decided steppe plant in its chief distribution, has a very re- 

 markable distribution area on the shores of South-Eastern Sweden, Southern Den- 

 mark, and Southern Finland, the only one outside the steppes. It occurs here on 

 rocky islets, skerries etc., frequently in places rich in guano, where it is able to 

 grow, probably because it is free from the struggle for space with stronger species. 



If the likewise decided steppe plant Isatis tmctoria is to be looked upon as 

 spontaneous in South Sweden, its occurrence is to be placed side by side with 

 that of Silene viscosa, but it occurs chiefly on sandy or gravelly sea-shores. 



Concerning the species now mentioned, their mode of occurrence in South 

 Sweden coincides rather well with their rich distribution on the South European 

 steppes (compare above p. 281). 



Viola piimila has on Oland and Gotland, as generally outside Pontis, a mode 

 of occurrence that does not correspond to its character of steppe plant. On the 

 Alvar it occurs in damp places — damp at least during periods of precipitation 

 and especially in spring — partly in crevices in the limestone together with 

 hydrophilous or mesophilous plants, partly in rather hydrophilous meadows where 

 the main part of the vegetation is formed of Sesleria coerulea, Carex panicea, 

 glauca and Hornschuchiana. However, I once saw the species on the Alvar of 

 Oland occur in a strongly xerophilous vegetation, Helianthemum oelandicum- 

 Cetraria islandica — heath (compare above p. 282). 



Melica ciliata in South-Eastern Sweden belongs to the sparse colony-like vege- 

 tation on precipitous cliffs and rocky ground, as is generally the case outside the 

 steppes. 



Concerning the mode of occurrence of the steppe species in South Sweden, it 

 appears from what has been said that it generally agrees well with the occurrence 

 of the species in the steppe vegetation. Species belonging to the strongly xero- 



