ON VARIATION GENERALLY. 
23 
the frond itself, which may have overlapping or distant sub- 
divisions (pinnae, pinnules, or pinnulets, according as they^ 
form first, second, or third divisions), all of which affect the 
result so much that the eye can easily distinguish the 
differences which characterise many variations of the same 
normal form. This cresting, in one or other of its forms, is 
the characteristic of the major number of known varieties. 
Plumation . — This is by some considered — and with reason 
— ^the most beautiful type of variation. It consists either in 
a much more delicate division and growth of the ultimate 
sections of the frond or in a greater foliaceous development, 
the result being as great a difference between the common 
and the plumose forms as that between a goose-feather and 
an ostrich-feather amongst the divided Ferns, such as the 
Lady Fern, the Male Fern, &c., and between a plain strap | 
and an elaborate, fringed frill in the case of the Hartstongue I 
type. In this class of variation the normal outline of the / 
fi’bnd is maintained, or merely widened, except, of course, • 
where it is combined with cristation, which is frequently the \ 
case. ' 
The plumose character is usually accompanied by partial 
or entire absence of spores, the reproductive vigour of the 
plant suffering, apparently, at the expense of its leafy 
development, precisely as in the case of double fiowers, to 
which it probably furnishes a parallel. There seems, however, 
good ground for the belief that, though spores are not 
formed, or very sparingly, the reproductive powers of the 
plant are enhanced in other ways, such as by the production 
of buds, latent or evident, on various parts of the fronds. 
From experiments, we find that the barren Hartstongue— ^ 
i.e., the crispum or frilled section — can be propagated much ^ 
more freely from sections of the bases of the frond stalks - 
than is the case with the fertile varieties. This would har- ! 
monise with Darwin’s hypothesis of pangenesis, and suggests , 
the advisability of a closer investigation of the so-caUed I 
barren forms generally. 
Dwarfing and Congestion are self-descriptive terms. Some of 
the dwarfed forms are extremely pretty, and specially adapted 
