*5 



CHAPTER III. 



GEOGRAPHICAL DISTRIBUTION. 



rjlHE known limits of the genus, which is confined to the Old World in the 

 -L northern hemisphere, may be approximately stated to be between g° W. and 

 87° E. longitude, and 55 N. and 31 N. latitude: the main eastern limit being 50 E. 

 longitude, and the main northern limit 50° N. latitude — the occurrence of C. alatavicus 

 in the Ala Tau mountains of Central Asia carrying the genus far north-east of the 

 general area of distribution. C. Chtsii, in Portugal, is the most western species; 

 C. hyemalis, in South Palestine, the most southern species at present known ; and 

 C. Salzmanni, the most south-western species. 



The area of distribution would roughly centre round the Mediterranean and 

 Black Sea coasts, though it does not form an essential feature of what is known 

 as the Mediterranean Flora, many of the species ascending to high ranges of altitude. 



The accompanying tables represent the range in latitude, and the range in 

 longitude of each species; and the diagrams the number of the species occurring 

 at each degree of latitude and of longitude. 



At longitude 24° East, nineteen species occur, a somewhat larger number than 

 occur to the east or west. 40° North, is pre-eminently the latitude in which the 

 greatest number of species occur, and here we have no less than thirty out of the 

 sixty-nine known species, and both north and south of this zone the numbers 

 rapidly fall off in fairly regular steps. The average range of individual species 

 in latitude is somewhat over three and a half degrees, or about two hundred and 

 fifty miles; and in longitude, somewhat over six degrees, equivalent to three 

 hundred and forty miles in latitude 40. 



The proportionate range in latitude and longitude of each individual species 

 is very variable; but it will be noticed from the tables that exceptionally great 

 ranges in longitude are more frequent than in latitude. 



A parallelogram of the proportions of Fig. 12. represents the relation of latitude 



E 



