







54 BRITISH FERNS 
edge, may vary into “ crenate,' with slightly projecting lobes, 
“serrate,” sharp and obvious ones, and so on through bi-pinnate, 
or twice-divided fronds, away into such finely dissected or much- 
cut forms as we see in P. v. Cornubiense, or in the various forms of 
the Welsh Polypody (P. v. cambricum) (see Appendix for numerous 
examples). In numerous Shield Ferns (Polystichum) we see this 
same principle carried out, often in association with extremely 
varied shapes of the pinnules, altering greatly the aspect of the 
plant. By virtue of this tendency to greater division of a normally 
bi-pinnate or twice-divided species, we have tri-pinnate, quadri- 
pinnate, and even quinque-pinnate forms, and in most of these 
extreme cases the subdivisions, though becoming slenderer and 
slenderer, are still seen to adhere to the peculiar specific mitten- 
shaped form if closely inspected, i.e. like a fingerless glove, with 
the thumb projecting at an obtuse angle. In the extraordinary 
gracillimum section of P. aculeatum recently raised, it is, how- 
ever, impossible to trace this form, the normal half-inch pinnule 
being lengthened to between two and three inches, and corres- 
pondingly narrowed (Figs. тт, 12, 13). In the Hartstongue the 
plain, undivided strap-like frond, when inspired by Nature to 
“ sport ” in the same direction, is somewhat baffled by its shape 
from taking it, but finds a way out by forming deep frills (S. v. cris- 
pum), its free veins, which fork once or twice normally on their way 
to the frond edge, forking over and over again as they approach it, 
carrying the tissue with them, the result being edges two or three 
times as long as the frond, and a consequent folding over, which 
renders this section a very handsome one, some of the members of 
which have invented a further outlet for their superabundant 
energy by providing the frills with fringes. Others of this species 
have not been baffled entirely in the ordinary direction of greater 
division, but have gone far in the direction of the pinnate Ferns 
by producing boldly-toothed and deeply-cut edges (S. v. projectum). 
The true plumose or extra feathery Ferns embrace the frilled 
Hartstongues, and such much-divided members of other species 
as are barren of spores, such as the cambricum Polypodies, Asplenium 
trichomanes incisum, S. v. сизфит aforesaid, Lastrea montana 
plumosa, and others, to which must be added on the score of beauty 
a number of Polystichums and Lady Ferns treated of elsewhere, 
which, despite a certain amount of fertility in spores, rank with 
the most beautiful feathery varieties in the world. A very curious 
type of variation is seen in a number of the divided Ferns, which 15 
presumably akin to the sagittate, ог arrow-shaped Hartstongues. 
These forms are termed deltoid, or triangular, or brachiate, accord- 
ing to the extent to which the variation goes. In the Appendix, 
a number of marked forms of Polypodiwm vulgare, Polystichum 
angulare, and Scolopendrium vulgare are shown of this type, in 
which the lowermost divisions are greatly lengthened, widening the 

