DR. HOOKER ON THE DISTRIBUTION OF ARCTIC PLANTS. 259 



Scandinavian forms ; for these belong to the remotest corner of the Scandinavian area, 

 and should of all plants be the most impatient of temperate, warm, and tropical climates. 

 The following will, approximately, express the result : — 



Total Arctic Scandinavian forms .... 586 Cross Aljjs, &c 480 



In North United States and Canada, &c. . 360 Reach South Africa 20 



In Tropical America 40 Himalaya, &c 300 



In Temperate South America 70 Tropical Asia 20 



In Alps of Middle Europe, Pyrenees, &c. . 490 Australia, &c 60 



In one respect this migration is most direct in the American meridian, where more 

 arctic species reach the highest southern latitudes. This I have accoimted for (Flora 

 Antarctica, p. 230) by the continuous chain of the Andes having favoured their southern 

 dispersion. 



But the greatest number of arctic plants are located in Central Europe, no fewer than 

 530 out of 762 inhabiting the Alps and Central and Southern Europe, of which 480 cross 

 the Alps to the Mediterranean basin. Here, however, their further spread is apparently 

 suddenly arrested ; for though many doubtless are to be found in the Alps of Abyssinia 

 and the western Atlas, these are few compared with what are found further east in 

 Asia ; and fewer still have found their way to South Africa. 



The most continuous extension of Scandinavian forms is in the direction of the greatest 

 continental extension ; namely, that from the North Cape in Lapland to Tasmania* ; for 

 no less than 350 Scandinavian plants have been found in the Himalaya, and 63 in 

 Australia and New Zealand ; whereas there are scarcely any Himalayan and no Austra- 

 lian or Antarctic forms in Arctic Europe. Now that Mr. Darwin's hypotheses are so far 

 accepted by many botanists, in that these concede many species of each genus to have had 

 in most cases a common origin, it may be well to tabulate the generic distribution of 

 arctic plants as I have done the specific ; and this places the prevalence of the Scandina- 

 vian types of vegetation in a much stronger light : — 



Scandinavian Arctic Genera in Europe . . 280 Cross Alps (approximately) 260 



Found in North United States (approximately) 270 Found in South Africa (approximately) . .110 



„ Tropical American Mountains „ . 100 „ Himalaya, &c. „ .... 270 



„ Temperate South America „ .120 „ Tropical Asia „ .... 80 



„ Alps „ . 280 „ Australia, &c. „ .... 100 



The most remarkable anomaly is the absence of Primula in Tropical America, that 

 genus being found in Extra-tropical South America; and its absence in the whole 

 southern temperate zone of the Old World, except the Alps of Java. 



* The line which joins these points passes through Siberia, Eastern China, the Celebes Islands, and Australia, 

 but the gl.arial migration has no doubt been due south from the arctic and north temperate regions in various 

 longitudes to the Pyrenees, Alps, Carpathians, Caucasus, Asia Minor, Persian and North Indian mountains, kc. The 

 further migration south to the distant and scattered alpine heights of the tropics, and thence to South Australia, 

 Tasmania, and NewJZealand, is, in the present state of our knowledge, to me quite unaccounted for. Mr. Darwin 

 assumes for this purpose a cooled condition of the globe that must have been fatal to all such purely tropical vegeta- 

 tion as we are now familiar with. 



VOL. XXIII. 2 N 



