370 CHARACTERS OF TRIRES AND GENERA, 
zones. B. ternatum and B. Virginica have also a wide 
geographical range, being found very generally throughout 
the temperate and tropical zones; the influence of the 
various climates causing much variation in the more or 
less divisions of the fronds, many of the states having 
been described as distinct species. 
Presl describes no less than seventeen species, which 
in the “Synopsis Filicum ” are reduced to six. 
Total number of species quoted, 1815. 
