ON THE DISTRIBUTION OF PLANTS. 199 
and birds; migrating birds, according to Prof. Collett, being com- 
monly insectivorous, the resident birds are of greater importance 
history of our flora must be considered. ological revolutions of 
the past are reflected in the vegetation of the ae we must try 
to read eed a eaice rightly what the plants tell. 
n shown above that the diaeibuiian of plants seems to 
Saisie. that geographies! changes between sea and land have taken 
lace in recent geological time. We will now look at the climatic 
geographien lo 
ing how Speste the present distribution depends on climate, 
we steal ubt that a similar dependence prevailed in bygone 
days. In si pen, too, the distribution was regulated by climate, 
soil, struggle with competitors, &c. Change of climate is the main 
cause of change of distribution. Such es of climate were the 
fooaidica, and of changes of distribution i in differant ¢ The 
observations of to- ee show that common one whisk are 
peculiarly favoure mate are __ not at all particular about 
found.i in a certain sort of habitat. If ase is altered, the com- 
monest species have the greatest probability of surviving the 
change. We find near ergs mam especially in the subalpine 
region, still some of our coast plan As I shall show hereafter, 
eoee. are shai survivors of a si age. rt these survivors 
sti w in the lowlands belong, too, to the t 
d amongst the heat-loving lowland plants the most com- 
mon regularly go farther west e the climate should 
colder, Feet species would by degrees become extinct. 
screes, on lime no cosas &c, And if the climate should become 
warmer, <Seewi species would survive, especially in cool damp 
la 
s. 
Dr. R. Hult, of Helens a treated the distribution of 
plants (phenogamous and mos n Finland and South Sweden 
in several interesting essays. He aa studied those changes in the 
distribution of iene which are going on, as it were, before our 
eyes. Local changes may in a moment destroy, partially or ee 
the vegetation dn a place; the burning of woods, the inundations 
rivers, and the abandonment of cultivated ground, are causes of oe 
changes. He distinguishes between changeable and unchangeable 
