THE CONTINENTAL FLORA OF SOUTH SWEDEN 233 



In order to furnish an idea of the way in which the continental species occur 

 in the vegetation, five of the above-mentioned special districts have been inves- 

 tigated in order to show how continental species are represented in different types 

 of vegetation. 



The statements in floristic works regarding the mode of occurrence are the 

 only material that can be obtained for these statistics. Hence the types of ve- 

 getation must be units of a very high rank: they are the main types of the 

 vegetation. They have been delimited with regard to the existence and strength 

 of continental features in the character of the vegetation, above all the xeromor- 

 phous structure and the heliophily of the species. 



The types of vegetation are as follows: 



1. Xerophilous herb and grass associations: steppe associations, the »Trift-for- 

 mation», »rock-ground associations*, »herb» or »grass heaths», »waste herbage» etc. 



2. Open Scotch pine forest associations on dry sandy soil with a ground vegeta- 

 tion of sand-grass heaths, often rich in herbs. {This type of vegetation seems to 

 have a decidedly continental distribution. Sand-grass heaths, rich in herbs, reach 

 farther west.) 



3. Open xerophytic foliferous forest and bush associations : » Steppe woods*, 

 »rock-groundwoods»,drywood-edges, scrub associations(Svved. »backsnar jand soon. 



4. Mesophytic grass and herb associations: flood meadows, certain cultivated 

 meadows. 



5. Closed coniferous forests (especially Scotch pine forests): coniferous forests 

 rich in mosses and undershrubs. 



6. Mesophytic foliferous forests with not very shady wood-layer: birch-, aspen- 

 and oak-forests, mesophytic wood-edges, forests of type 7 thinned by human activity. 



7. Mesophytic foliferous forests with heavily shady wood-layer: beech-forests, 

 certain mixed deciduous forests: »groves», Swed. »lundar». Germ. »Auenwalder», 

 »Gemischte Laubholzformationen der Niederung und Hugelregion» Drude 1896, 

 »Der mitteleuropaische Eichenmischwald» Sernander igo6, p. 372; Hayek 1916, 

 and so on. 



8. Helophytic grass and herb associations: n\3.xs\\ associations. Here are also the 

 reed associations to be placed (compare Warming 1909). 



9. Aquatic associations : associations of freely swimming species or of species 

 whose assimilatory organs are submerged (compare Warming 1. c). 



10. Moor-associations: Sphagnum-moors, forest-moors (compare Warming 1. c). 



The statements of floristic works have not always furnished sufficient informa- 

 tion, and consequently the statistics cannot claim complete accuracy. — The 

 same species can, of course, form part of more than one type of vegetation. In 

 such cases the species have been placed with the type where their normal exist- 

 ence seems to be. Some species, however, have been placed with two types. 



