290 RIKARD STERNER 



stifolia, Polytrichum juniperinum, Thuidium abietinuin, Cetraria islandica, 

 Cladina silvatica, Cladonia rangiformis, and Peltigera canina. (See Table 2, 

 Appendix II.) 



Of steppe species that may occur in the Subatlantic types in South- 

 Eastern Sweden, we notice Potentilla arenaria (Blekinge and Smaland), 

 Phleum Boehmeri (especially Ostergotland and Uppland), and Trifolium 

 montanum. 



For a close study of the mode of occurrence of steppe species in South Sweden a 

 fairly considerable material of vegetation analyses has been collected. Tables i — 3, 

 Appendix II, contain extracts from this material. The scope of the present work does 

 not allow of the publication of the whole material. 



It is important to point out that these vegetation-analyses are not meant to examplify 

 the established types in their typical composition; the analyses have been carried out onlv 

 to shozv /i07v steppe species occur in South Sivedish vegetation. I have tried, however, to 

 arrange the analyses according to the above grouping of the vegetation-types, though 

 in many cases they form transition types. 



Nor are the analyses suited to form bases for a description of plant associations 

 according to modern principles. It is true that the experimental areas have always been 

 distinctly limited, but the size of the areas used has varied a great deal, because some 

 analyses were carried out several years ago (19 16 and 19 17). 



My analyses partly concern great areas with homogeneous vegetation, which have 

 been fully analysed, by means of a great number of smaller squares of a certain size 

 (i or 4 m^) and placed in a certain unit, partly similar smaller squares chosen 

 sporadically one by one in different places in a similar, homogeneous vegetation. The 

 great majority of these isolated smaller areas also are of one or four square metres. 



The first-named analyses are denoted in the tables by Latin figures. In these columns 

 the number of squares in which a species is found, are given with percentage figures 

 {the individual freqicencv of the species). With Latin figures (or the sign of X ) are in 

 these columns given also the coefficients of the average area which is covered by a 

 species, the >^Arcalprozent7> or yytlie degree of covering of the species^. The degree of co- 

 vering is judged according to the Hult-Sernander scale of five degrees. (About the 

 principle of this method see Du Rietz 192 1, pp. 224 ff.) This five-degree scale, how- 

 ever, has been enlarged with the sign of x , which signifies that a species occurs quite 

 slightly, only in one or two individuals, and with one degree between I and II, marked 

 I-f, and one between II and III, marked II -f. — The statements about the covering- 

 degree of species in these analyses always refer to experimental areas of one square 

 metre. 



By means of experiments I have found that, with regard to these vegetation types, a 

 good idea of the character of the vegetation is generally obtained with experimental 

 areas of four square metres. If the experimental areas are made larger, the increase 

 in the number of species becomes so inconsiderable that the said size ought from a 

 practical point of vieiv to be the one most suitable for the object in question. On the 

 other hand, I do not wish to maintain the opinion that this area should be the tninimum 

 area of the association [the t> Minimiareal * : i>das kleinste Ateal, auf ivelchein die Assoziation 

 ihre definitive Anzahl Konstanten erreicht-%, Du Rietz, Fries, Osvald und Tengvall 1920, 

 p. 35; Du Rietz 1921, p. 146). Even with an experimental area of one square metre, 



