59 ° 
Sinnott and Bailey . — The Origin and 
Such conditions would tend not only to produce a very rich and varied 
flora, but also, as Darwin has pointed out, the great competition involved 
would make its members hardy and able to thrive under all sorts of con- 
ditions. Wallace has remarked upon ‘the wonderful aggressive and 
colonizing power of the Scandinavian flora, as shown by the way in which 
it establishes itself in any temperate country to which it may gain access’. 
It should be noted, however, that the members of the northern flora which 
exhibit this aggressiveness, and which are widely distributed as weeds and 
common plants all over the world, are all herbs ! 
Our next task will be to trace, if possible, the dispersal of this dominant 
herbaceous flora from the northern continental areas in which it arose into 
the distant southern lands where now it flourishes. These antipodean 
colonies are at present isolated from their northern congeners by many 
degrees of latitude, a circumstance for the explanation of which various 
hypotheses have been put forward. 
The theory which regards these plants as representatives of an ex- 
ceedingly ancient type of vegetation which has long since been exterminated 
everywhere save near the poles, has not only to meet the botanical evidence 
which indicates that herbs in general are of recent origin, and that their 
arrival in the extreme south has occurred in relatively modern times ; but 
also the geological evidence that Australasia, South America, and Southern 
Africa have been open to immigration for only a comparatively short time. 
If we admit that the invasion of the south temperate regions by an 
herbaceous flora from the north took place at a relatively recent date, 
geologically speaking, it is evident that this invasion must have crossed the 
tropics along some range of mountains where approximately temperate 
conditions would obtain. The question of the routes along which this 
southward migration occurred has been discussed by Wallace, who brings 
forward evidence that it has proceeded over three main courses — the central 
African highlands; the Himalayas, Malay Peninsula, and East Indies; 
and Central America and the Andes. 
Only the last of these now presents an unbroken chain of highlands 
from north temperate lands to high southern latitudes ; and scattered 
throughout its length are many northern genera and species, although even 
here there are usually wide gaps between the northern and the southern 
ranges of the same species. Along this route it is obvious that the northern 
flora must have reached Chile, Patagonia, and Fuegia. The close resem- 
blance of these northern plants in the Patagonian region to those of 
New Zealand, Tasmania, the south-eastern portion of Australia and the 
Antarctic islands — a resemblance often extending to identity in species, and 
one which is shared by the endemic flora as well — makes it very probable 
that an interchange of plants between these various regions was possible in 
former times. In fact, the existence of an Antarctic continent well stocked 
