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. Comubiense, 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, n, 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. crispum 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 is 

 presumably akin to the sagittate, or 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 Polypodium vulgare, Polystichum 

 angular e, and Scolopendrium vulgare are shown of this type, in 

 which the lowermost divisions are greatly lengthened, widening the 



