332 FIRST FORMS OF VEGETATION. 
tudes, where the temperature is mild and genial, 
and where there is a constant supply of moisture. 
Professor Fries of Upsal, the presiding genius of 
these plants, gathered in Sweden, within a space 
of ground not exceeding a square furlong, more 
than two thousand distinct species. ‘This coun- 
try, says Mr. Berkeley, ‘with its various soils, 
large mixed forests, and warm summer tempera- 
ture, seems to produce more species than any part 
of the known world; and next in order, perhaps, 
are the United States, as far as South Carolina, 
where they absolutely swarm. A moist autumn 
after a genial summer is most conducive to their 
growth, but cold, wet summers are seldom produc- 
tive. The portion of the Himalayas which lies 
immediately north of Calcutta is perhaps almost 
as prolific in point of individuals as the countries 
named above, but the number of species on ex- 
amination proves far less than might at first have 
been suspected. It is probably not a fifth of what 
occurs in Sweden. Great Britain, though possess- 
ing a considerable list of species, is not abundant 
in individuals, except as regards a limited number 
of species. The exuberance, even in the most 
favourable autumn, is not to be compared with that 
of Sweden or many parts of Germany.’ They are 
found in the Arctic and Antarctic regions, almost 
as far as the limits of vegetation. They penetrate 
