( 4 ) 
It must be distinctly understood that the previous 
numbers refer only to ferns of the British Isles, as 
many other genera of these three Groups exist in 
foreign countries. In the following descriptions the 
genera and species are arranged alphabetically. 
GROUP I. 
POLYPODIACEjE. 
Vernation. Circinate, the young fronds coiled up like 
a watch-spring. (See page $ 7.) 
Thecae. Dorsal or marginal, each enclosed by an elastic 
ring which bursts when mature and scatters 
the spores. This ring is vertical, excepting 
in the genera Hymenophyllum and Tricho- 
manes. 
GROUP I; GENUS I. 
ADIANTUM. 
Sori. In roundish masses, growing from the ends of 
the venules on the reflexed membranous 
margin of the pinnules. This membrane is 
prolonged over the sori, and forms the in- 
dusium. 
Venules. Free. 
