THE CONTINENTAL FLORA OF SOUTH SWEDEN 231 

 special districts on the Middle European plain. 



common lo two special districts 



Silesia Brandenburg South Sweden 



Total 



o 



tal 

 numljer 



I 



% 



numoer 



% 



Total 

 number 



% 



Westphalia 



Total 

 number 



Northern 

 France 



Total 

 number 



Number of conti- 



"t; — -r : nental sijccies in the 



bouth-eastern ' 



England 



/o 



Total 

 number 



special districts 



% 



Total 

 number 



620 

 730 

 760 

 946 



970 

 800 

 820 



S47 



725 



283 

 230 



135 

 187 



195 



160 



"5 

 70 



54 

 12 



the map of the soil-types in Ramann I9ii,p. 561): Hooker 1884, Watson 1883 

 — Of the provinces into which Watson has spHt up Great Britain, those he names 

 Channel, Thames, Ouse, and Trent form the district in question. 



In the statistics all those species have been excluded whose occurrence is decidedly 

 dependent on the activity of man; that is to say, all casuals, all introduced and na- 

 turalized species and all species that occur only in cultivated fields, at roadsides 

 and in other waste places etc. (»aiiens», »colonists» and so on). Naturally it is some- 

 times difficult to judge if a species has been introduced by man, or if it is a real 

 native, solely by means of the statements of floristic works. Hence the statistics 

 cannot claim complete exactness. Some uncertainty in the calculations is also 

 caused by the different modes of treatment of critical groups of species in diffe- 

 rent floristic works. To get the numbers of species as comparable as possible, 

 the species have in such cases been taken very collectively, or they have been 

 quite excluded. 



The statistics have been brought together in Table i, where there is also a 

 list of the number of continental species in the special districts. From this table 

 it appears in the first place that there is a probably unexpectedly great coinci- 

 dence between tlie floras of the special districts. In most cases the percentage 

 of species common to two special districts keeps between 70 and go, only in six 

 cases does it sink below 60. Furthermore the comparatively great uniformity is 

 shown by the number of species common to all the districts, which has been 

 found to be about 435, forming 25% of the total number of species; it is also 

 seen from the fact that the numiber of species occurring only in one special dis- 

 trict is only 230 (Kazan 58, Moscow 13, Livonia i, West Prussia 4, Silesia 27, 



