Chapter XI — 207 — Concept of Floral Elements 



testing of conclusions. Often an evaluation of an area is made without 

 going into the history of the formation of the area itself, the flora of 

 Europe, for instance, being taken as a starting point, with which flora 

 the species of the given flora are compared. Thus, Hooker (1855) 

 finds in the flora of the Himalayas and northern India a European 

 element only because the species forming it are hkewise found in the 

 flora of western Europe, although, of course, it is perfectly clear that 

 the centers of areas of these species lie precisely in the Himalayas, 

 whence in post-glacial times they spread to Europe. Hence, this ele- 

 ment might be designated as Himalayan in the flora of Europe but in 

 no case as a European element in the flora of India. 



We shall now take up individually some of the floral elements most 

 frequently encountered in analyses of the composition of floras from 

 the standpoint of historical plant geography. 



Geographical Elements: — 



1. The arctic-alpine element embraces a group of species having 

 areas with one part lying in the Alps and the other in the Arctic. 

 These two parts, now separated by the entire breadth of the subarctic 

 zone and the greater part of the north temperate zone, were during the 

 Ice Age in juxtaposition. At present only in a few places do mountain 

 chains stretch from the Arctic zone far to the south, as, for instance, 

 the Rocky Mountains in North America, the Urals in the U.S.S.R., 

 and the Stanovy Mts. in northeastern Siberia, thus forming a bridge 

 between the arctic and alpine parts of the areas of species of this ele- 

 ment. By ascertaining the origin of the various species belonging to 

 this element and dividing them into an arctic and an alpine group, we 

 may distinguish between genetic-alpine and genetic-arctic elements. 



2. The subarctic or subarctic-mountain element (Stefpen, 1935) 

 embraces species distributed along the border between the forest and 

 the tundra zone. Some species distributed in the subarctic zone are 

 also found in mountains, these forming a subarctic-mountain element. 

 Here we may also refer subarctic steppe species that penetrated into 

 subarctic regions presumably in arid, post-glacial times. 



3. The pontic clement was first introduced as a term by Kerner 

 (1887), who gave it a purely geographical characterization. He under- 

 stood by it "the very unique flora that spread from the northern and 

 western shores of the Pontic [Black] Sea westward over southern 

 Russia and the northern part of the Balkan Peninsula, the Danube 

 region, Siebenbiirgen, and Hungary as far as the Alps and the Car- 

 pathians". Steffen (193s) has made more precise the boundaries of 

 the range of this group of species. On the south this range begins with 

 the northern spurs of the Caucasus Mts. and the northern shore of the 

 Black Sea, excluding Crimea (which he refers entirely to the Medi- 

 terranean region); on the north its boundary lies where the steppe 

 merges into mixed oak forests; on the west this range embraces the 

 Rumanian steppes and the Hungarian lowlands. As regards these 

 three boundaries all investigators are in agreement, but this is not the 

 case as regards the eastern boundary. In view of the fact that species 

 of the pontic group are primarily xerophytes distributed far to the east 

 within the limits of the steppe zone, some investigators have set its 



