336 PLANTS, SEEDS, AND CURRENTS 



American species tells a story of the stream from the north; and, 

 since nearly all of them are also Eurasian, we find a noticeable pro- 

 portion of Old World forms amongst the species migrating south. 

 In both there is a connection with Africa of the slightest kind. In 

 both also there is apparently an Australian and a New Zealand 

 connection. 



The links of South America with the outside world, as exemplified 

 by the Peat-mosses and the Carices, are here tabulated in a general 

 way. There are about 110 species of Sphagnum and rather over eighty 

 species of Carex known from this continent, of which in the first case 

 eleven species and in the second case twenty-nine species occur 

 outside it. Since the same species is usually recorded from more 

 than one region, the totals here given exceed the number of species 

 concerned. 



The Distribution of the non-Endemic South American Species of 

 Sphagnum (11) and Carex (29) 





Sphagnum 



Carex 



North America 



7 



18 | 



Eurasia 



6 



11 



Sphagnum — 6 in Europe, 4 in Asia. 

 Carex — 10 in Europe, 11 in Asia. 



Central America 



5 



11 





Australia and New 

 Zealand 



2 



6 





Africa 



1 



1 



The Sphagnum species occurs in 

 Central Africa. The Carex species 

 occurs in South Africa. 



The facilities offered to migration from the north to the south by the 

 great mountainous backbone of the western world and the results aris- 

 ing have often supplied themes to the botanist. An almost unbroken 

 chain of mountains and highlands, connecting Arctic and Antarctic 

 lands, is to be found in the American continent, and there alone on 

 our globe. The only break of importance in this great continuous 

 mountain chain lies, writes Harshberger (p. 191), in the Isthmus of 

 Panama, where there is a distance of about 300 miles occupied by 

 rugged forest-clad hills, between the lofty peaks of Veragua and the 

 northern extremity of the Andes in New Granada. We should 

 accordingly expect, as this writer proceeds to say, that this great chain 

 would form the most effective agent in aiding the southward migra- 

 tion of the Arctic and north temperate vegetation. In other words, 

 the plants of the north would have often followed this route south- 

 ward along the lofty mountains and elevated uplands; and "we 

 do find," as the same author continues, " not only that a large number 

 of northern genera and many species are scattered along this route, 

 but at the end of the long journey, in Southern Chili and Fuegia, 

 they are found in numbers sufficient to form an element in the 



