STRUCTURE 
17 
every damp surface, either of earth, stone, or rock. As the 
rootlets acquire age, they become oftentimes tough and wiry, 
insinuating themselves into the tiniest crevices, and often 
extending their progress to considerable distances from the 
root-stock. Should the situation of the plant he such that 
possible drought might deprive it of moisture, the rootlets, 
as if by instinct, penetrate deeply into the earth, bank, or 
rocky seam, in search of distant and moister crevices than 
those in the immediate vicinity of the caudex or rhizoma. 
I11 such cases, and after a Fern has remained undisturbed 
for years, the great mass of these delicate fibres, ramifying 
in all directions, constitutes a marvellous and beautiful 
system, built up as a protection against the plant’s great 
foe — drought. 
Before we conclude our remarks on the root-stocks of 
Ferns, let us notice those which in a large number of the 
species are upright in form, and raised above the surface of 
the ground. Sometimes — and indeed in the majority of 
instances — they are raised but slightly, often not more than 
an inch above the ground level or bank on which they are 
growing. The upper portion of the root-stock is in such 
cases formed into a crown, which is the basis from which the 
fronds spring. The crown is practically formed of a circle, 
or circular cluster of fronds, of the bases of fronds in a fully- 
developed plant, and of the buds merely of the fronds in an 
undeveloped or unopened state. Of the position and arrange- 
ment of the fronds we shall have more to say anon. Here 
we have only to explain how the elongation of the crown is 
caused. Each year’s circlet of fronds as it decays leaves the 
bases of its stems upon the crown of the plant. These stem- 
bases, rising each year one stage higher, gradually heighten 
the crown, the various sets of fronds all leaving their lower 
parts in continuation of the process. We have already seen 
that this process is carried on oftentimes, where the con- 
c 
