4f)'2 DISTRIBUTIOX OF RECENT FERNS. 
The total known number of existing species of 
Ferns is about 1500. These admit of a threefold 
geographical distribution : 
1 . Those of the temperate and frigid zone of 
the northern hemisphere, containing 144 species. 
2. Those of the southern temperate zone, in- 
cluding the Cape of Good Hope, parts of South 
America, and the extra-tropical part of New Hol- 
land, and New Zealand, 140 species. 
3. Those which grow within 30 or 35 degrees 
on each side of the Equator, 1200 species. 
If we compare the amount of Ferns with the 
united numbers of other tribes of plants, we may 
form some idea of the relative importance of this 
family in the vegetation of the district, or period 
to which we apply such comparison. Thus, in 
the entire number of known species of plants 
now existing on the globe, we have 1500 Ferns 
and 45,000 Phanerogamiae, being in the propor- 
tion of 1 to 30. In Europe this proportion varies 
from 1:35 tol:80, and may average 1:60. Between 
the Tropics, Humboldt estimates the number in 
Equinoxial America at 1:36, and Mr. Brown 
gives 1:20 as the proportion in those parts of 
intertropical Continents which are most favour- 
able* to Ferns. 
Mr. Brown (Appendix to Tuckey's Congo 
Expedition) states that the circumstances most 
* Botany of Congo, p. 42. 
