Relation of Climate to Vegetation. | nly 
Another fact that may be noted in this connection, is 
that plants of a more southern type not infrequently 
ascend to higher latitudes, and thus occur beyond the gen- 
eral limit of distribution for the species as a whole. This 
finds its explanation in part in the fact already cited, that 
great plateaus have a somewhat higher temperature than 
isolated mountains at the same elevation, but it is also to be 
referred in part to other causes. Such northern extensions 
of a flora will be found to be accomplished under the pro- 
tecting influence of large bodies of water, which secure a 
more equable temperature, and tend to produce a somewhat 
higher annual mean than in more remote parts in the same 
latitude and at the same elevation above sea level. Warm 
ocean currents have a similar effect, and often produce the 
most striking modifications in the climate and vegetation of 
the shores they wash. 
In the Atlantic, the Gulf Stream sweeps along the coast 
of Newfoundland, and reaches across to the northern shores 
of Great Britain, and even of Norway, giving to the former 
a climate whose mean annual temperature is that of New 
York, and a vegetation which, on this continent, flourishes 
only at several degrees lower latitude. 
But if it is possible for such northern extensions of a 
flora to be made under special conditions, it is equally true 
that southern extensions of northern floras are possible. A 
notable instance of this is found in the arctic plants which, 
under the influence of the polar current reaching southward 
out of Baffin’s Bay, extend along the coast of Labrador and 
into the Gulf of St. Lawrence along its northern shores, 
thus intruding an arctic flora into the north temperate 
flora. 
As, however, an increase of temperature is, in general, 
more favorable to vegetation, it is found that plants more 
readily extend southward and adapt themselves to the 
conditions they there find, than in the opposite direction. 
Or to state it in a more practical way, plants may be trans- 
planted from a northern to a more southern region, with 
far greater assurance of successful acclimatisation, than if 
