THE CHRISTMAS AND HOLLY FERNS. 
OWEVER much we may admire the 
summer species, we can scarcely 
fail to have a higher regard for 
ae those sturdy ferns that remain 
oo pt 
eo through cold and snow to make the 
woodlands and thickets less dreary. 
For the most part they are among 
our coarsest species—delicate fronds 
have little chance against the frost 
—and for this reason are likely to 
be overlooked or neglected in a 
milder season. But when in dark and stormy weather 
the green fronds wave us a welcome from icy ledge or 
snowy thicket, the day seems suddenly to brighten. 
Foremost among our winter species must be placed 
the members of the Polystichum family. These are often 
classed with the wood ferns in the genus Aspidium or Dry- 
opteris. The wood ferns indeed are their nearest relatives, 
but there is this important difference between them: in 
the Polystichums, the sori are round and covered with a 
circular indusium which is fixed to the frond by its de- 
pressed centre; while in the wood ferns, the indusium is 
usually reniform and attached to the frond by the sinus. 
Like the wood ferns these species are sometimes called 
shield ferns and buckler ferns. 
