22 
CHOICE BRITISH FERNS. 
Another and very provoking form of inconstancy to which — 
especially amongst the soft prickly Shield Fern {PolysticJmm 
angulare) varieties — some of the best forms are liable, is a ten- 
dency to revert to the common form directly anything in 
the soil or treatment disagrees with them. They are then 
said to “ sulk ” ; and some most promising finds, having taken 
it into their heads — or, rather, crowns — to “ sulk ” in this 
fashion, have resisted all attempts to coax them into form ' 
again, and practically reverted altogether. 
We will now proceed to describe the more marked types 
of variation to which Ferns are subject, some of which seem 
quite peculiar to the family, and to have no parallels in other : 
plants. 
Cristation . — This consists in a multiplication of some or all 
of the extremities of the fronds and their subdivisions, form- 
ing a more or less heavy tassel. This ranges from a simple 
forking of the tip of the frond only, to an infinite division 
of all the parts, from the main stem upwards, and has been 
carried to such an extent in several species that, instead of ] 
a fiat, feather-like frond, we have apparently a ball of very | 
fine moss, all but resting on the soil. This cresting, which 1 
more commonly takes the tassel form aforesaid, is in its turn } 
varied infinitely in its character, not merely by the multipli- 
cation of the divisions which form it, but also by the mode | 
of such division. Thus, it may divide symmetrically in the j 
same plane, forming a wide or a narrow, fan-shaped crest; or | 
these divisions may be again subdivided symmetrically, at | 
greater or less distances, forming a flat lattice-work. Let, ,| 
then, each division be more or less twisted, and every degree 
of curvature will give a different effect; or the simple fan 
may be elongated, and the tips fanned out again. Here we i 
have, manifestly, already a great scope; yet this is doubled | 
by the capacity of the divisions to radiate, like the blossom | 
of a geranium (corymbiferous), with all the like variation ' 
repeated. The crests may also be formed by undivided ex- 
pansion of the tips — like a duck’s foot, instead of a crow’s, i' 
to give a familiar example. Then, again, all these combina- w 
tions are connected with the other varying characteristics of I 
