50-2 
GEOGRAPHY. 
BOOK V. 
From what has now been said, it would seem that the forms 
assumed by vegetation in different latitudes are dependent 
upon particular conditions of climate and soil, and that it is to 
variations of these conditions that we are to ascribe the differ- 
ence between the Flora of the equator and of the polar regions. 
And this is no doubt true : but there are, nevertheless, some 
plants which have a remarkable power of adapting themselves 
to all climates and circumstances ; and there are others which 
readily naturalise themselves in climates similar to their own. 
Of the latter, examples present themselves at every step ; all 
the hardy plants of our gardens may in some sort be con- 
sidered of this nature ; for although they do not grow spon- 
taneously in the fields, they flourish almost without care in 
our gardens. The pine-apple has gradually extended itself 
eastward from America, through Africa, into the Indian 
Archipelago ; where it is now as common as if it were a plant 
indigenous to the soil ; and in like manner the spices of the 
Indies have become naturalised on the coast of Africa and in 
the West Indian Islands. Of the former description the in- 
stances are not numerous, but they are very remarkable. In 
the woods of Georgia, in North America, gi'ows the Rosa laevi- 
gata, which, while all the other species of rose of that country 
are entirely different from those of other regions, is identical 
with the R. sinica of China ; to the Flora of which country 
that of North America has no resemblance. Samolus Valer- 
andi is found all over the world, from the fi'ozen north to the 
burning south ; associated here with Amentaceae and similar 
northern forms, and there mixed with palms and the genuine 
denizens of the tropics. Above 350 species are said to be 
common to Europe and North America, and even among the 
peculiar features of the Flora of New Holland, Brown re- 
cognised 166 European species. Royle has added numerous 
instances of Siberian, European, African, and American 
plants occurring in India. The presence of many of such 
strangers may undoubtedly be referred to the agency of man, 
by whom they have been transported from climate to climate, 
along with corn and by other means ; as, for example, at 
Pont Juvenal, near Montpellier, the vicinity of which abounds 
