952 PATAGONIAN EXPEDITIONS: BOTANY. 



seems to be at home in South Patagonia and Fuegia. The European Ulex 

 (furze] has been introduced, but it has a native congener in U. nanus. 

 Abrotanella unites, by closely allied species, New Zealand, Auckland and 

 Campbell's islands, South Australia and Magellan-Fuegia ; and Arte- 

 misia, a northern genus, has an outlying species in Chili-Fuegia. Several 

 northern forms are represented in the Patagonian region, yet remarkable 

 for their absence from Australasia. 



4. Instances of northward, or meridional, continuity are most numerous 

 and dominant ; not largely with Argentina, but chiefly with the Andine 

 region. Owing to the trend of the country and to the rivers flowing east- 

 wards to the Atlantic, there is a continual system of clearing out and re- 

 plenishing of plants. Floods exterminate the plants along the streams, 

 carrying them to the ocean ; and the vacated localities are soon populated 

 by new immigrants from the mountains. This system renders Patagonia 

 in large measure a botanical dependency on Chili ; and also a landing 

 place for immigrants from the far north, even from Mexico, California, 

 Alaska, and by the Bering route from Asia; apparently receiving from, 

 rather than contributing towards, the northern Floras. We find in our 

 list about 140 genera of flowering plants which have thus immigrated 

 southwards. It is about Magellan and Fuegia that there is least of this 

 change seen ; hence with these parts there is most permanency and most 

 characteristic peculiarity of forms. 



5. The eastward or latitudinal continuity is very limited, by reason of 

 the broad ocean ; and yet it is not inconsiderable. Patagonia, the Falk- 

 land Ids., Kerguelen, Australia, Tasmania, New Zealand, and the smaller 

 sporadic islands of the south, are correlated both botanically and zoo- 

 logically. It is a difficult question to find the conditions, and the lines 

 of movement of the colonization of each ; but that there has been an in- 

 terchange by land or winds or sea cannot be questioned. We find about 

 fifty genera represented in this transverse colonization. In some cases 

 the movement has been probably circuitous ; from an Asiatic center forms 

 migrated in opposite directions, some northward, and by trans-arctic land 

 or ice bridges to America, whence by the meridian route of the Western 

 Hemisphere they reached their goal in Patagonia; whilst others went 

 from their Asiatic source southwards by an Oriental meridian-line to 

 Eastern Australia, and so on. But a number of the forms that are com- 

 mon to Chili-Patagonia on one side, and to Australia-New Zealand on 



