A Dictionary of Choice Ferns. 
301 
POL,YPODl\JM— continued. 
where it makes most pleasing objects, tlie above mixture 
will be found equally suitable; but in either case avoid 
putting in too much soil; a depth of 3in. to 4in. is quite 
sufficient. It is also indiispemsable that thorough drainage 
should be secured^ for water remaining stagnant about its 
roots is very injurious to P. Dryopteris. In planting, great 
care must also be taken to prevent the rhizomes from being 
buried too deeply, in which case they Sieldoin grow ; they 
must be kept only just below the surface of the soil, through 
Fig. 115. Polypodium Heracleum, one of the most distinctive 
of all Polypodies. 
which it is advisable to allow the tips to protrude. Plant- 
ing should take place about April, and a moderate watering 
must follow, after which the soil requires to be kept con- 
stantly moist. Although totally deprived of foliage during 
four or five months of the year, the Oak Fern should never 
be allowed to get dry at the roots, for the rhizomes soon 
shrivel up and the spring growth then only produces small 
or deformed fronds, as the plants are much weakened. It 
is also advisable to give pot specimens a slight covering 
during the winter, though they do not require this 
attention when planted out. This species, readily increased 
by division, does not appear to have produced any constant 
variations ; though several more or less curious forms of it 
have from time to time been noticed. 
