ARCTIC AND NORTHERN FLORAS. 469 



north in America, and was driven southward as the glacial cold came 

 on. The northern flora is found in the mountains of Tropical Asia 

 as far south as India ; in the Abyssinian and Cameroon Mountains in 

 Africa ; in the Andes, to the extreme south of America ; and in a less 

 striking degree in the mountains of New Zealand, Tasmania, and 

 Victoria. This large flora has been divided by climatic zones into the 

 Alpino- Arctic, the cool temperate, and the Mediterraneo-Caucasian or 

 warm temperate floras. 1 



The Arctic Flora is very uniform. The birch is cultivated at 

 Reykjavik, but the summer is too short for its growth in Greenland ; 

 yet, owing to the influence of the continental mass of land, trees 

 flourish in Siberia as far north as 67 30'. On the eastern border of 

 the White Sea, lat. 65, peonies reach a large size, and aconites grow 

 equally well in the peninsula of Kola, lat. 64 ; while on the seashore 

 the smallest willows and herbs are found. Owing to the cold, the 

 roots of Arctic plants do not penetrate deep, but spread horizontally ; 

 thus the Valerian capitata and Salix lanata root differently in Kussia 

 and the Arctic regions. The fossil plants of the Arctic regions can in 

 no way be regarded as the progenitors of those now met with, for all 

 existing Arctic plants are stunted and have relatively large leaves. 

 Iceland possesses 450 vascular plants ; the west coast of Greenland, 

 323 ; Spitzbergen, 83.2 



The Northern Flora. In the western part of the Old World the 

 northern and tropical floras are widely severed by the great mountain 

 barrier which runs east and west, as well as by the African and 

 Arabian deserts. No tropical forms of vegetable life appear to have 

 crossed these northern barriers. In Central Asia the floras come 

 nearer together, and the Himalayan chain alone parts these types of 

 life, a few representatives of the tropical group extending into the 

 warmer valleys on the one side just as the northern life is found ex- 

 tending on the other side. In the extreme east this mountain chain 

 declines, so that there is no boundary dividing the two floras, and the 

 change from one to the other is gradual, so that in the Chino- 

 Japanese region the northern and southern types are blended, and 

 they form a distinct flora which has much in common with the 

 American flora. Thus the genera of eastern North America, Illicium, 

 Schizandra, Menispermum, Caulophyllum, Thermopsis, Podophyllum, 

 Amphicarpaea, Apios, Penthorum, Hamamelis, Dieroilla, Phryma, 

 Pyrularia, are represented in North-eastern Asia. 



In Europe the growth of wood begins in May and ends in August, 

 but in Siberia the larch has leaves for ten weeks only. On the Alps 

 it grows to a greater height than any other tree. The beech marks 

 climatic conditions in a striking way by its northern distribution. In 

 Norway it reaches latitude 59, passes the Swedish coast near Gothen- 

 burg, and crosses the continent from near Konigsberg to Podolia. It 



1 Grisebach : "Vegetation der Erde," 1872. 



2 Many of the plants mentioned may be studied in any botanical garden, but 

 the collections at Kew should be consulted. 



