GEOGRAPHICAL STATISTICS OF THE EUROPEAN FLORA. 23 
s 
read before your Society in 1873;* but the extension of the flora 
brought into consideration rendered some modification necessary. For 
ward beyond the limit of olive cultivation, but no e vine- 
yard boundary; and 3, Lower or Mediterranean, containing species 
confined within the region of olive cultivati e thus 
three lines of demarcation, the polar limits of ‘cereal cultivation, 
the vineyard line; zone 3, Zemperate, ranges both above the cereal 
line and below the vineyard line ; while of zone 4, Southern, the upper 
line, the mi section its 
upper limit in the vineyard line, and the lower section its upper limit 
det nt should properly be placed, 
altitude is of equal importance with latitude, as is evident from the 
reappearance of most high Arctic species on lofty mountains much 
further south. They are there accompanied by other plants whose 
North des hich Arctic plants extend. In the British 
ora are only two or three such Alpin , for a species 
reaches as far as Britain usually stretches further north to the Arctic 
in 
of Alpine plants increases so greatly as to exceed that of Arctic species, 
and it therefore becomes necessary to split up the Arctic zone into 
ree divisions—l, Arctic (restricted), for plants found only in the. 
extreme north ; 2, Aretic-Alpine, for those found on the mountains 
BO ! 
* See Journ. Bot., 1874, p, 84. eS meng Bolt 
