162 



KNOWLEDGE. 



[JoLY, 1902. 



Down. But more froqueiitly — and this is a very reuiark- 

 ablo fact — a liij;lil_v almorinal variety, soniotimos even oik- 

 fomliining Kirm-nl (Hiitc abnoruial features, will occur as a 

 sin;;le plant i^mwin^ amid normal I'nrius, and the most 

 careful search will reveal neither parent nor ofIs|)ring, in 

 spite of the high fertility of Ferns,* while in cultivation 

 it will ])ropa<j;ate freely and preserve its peculiar character. 

 That famous variety of the Lady Fern, A. F.-f.Vktnriw, to 

 be presently referred to (Fi<^. 3). thus occurred in Stirling- 

 shire — a form in which both the cruciate aud crested 

 characters are perfectly developed, and are constant in 

 the offsjiring. The equally remarkable A. F.-f. FrheUiiv 

 (Fig. 4), has been twice found — in Wicklow and in 

 Donegal — single plants in both cases, which can have had 

 no connection with each other ; and innumerable other 

 instances miglit be cited. 



The various British species differ enormously in their 

 tendency to vary. In the forefront of the variety-jiroducing 

 Ferns stand the Lady Fern, Male Fern, Soft Sliiild Fern, 

 and Hart's-tongue, each of which has yielded literally 

 hundreds of varieties. On the other hand, the Bracken, 

 Parsley Fern, Scale Fern, and Royal Fern, all of which 

 ai-e at least locally abundant, very seldom depart from the 

 normal character. In the Oak Fern, Limestone Polypody, 

 and many rarer species, varieties are unknown. 



Let us now see in what directions variation is most 

 marked, and through what species each type of variation 

 runs. The following classification is somewhat rough and 

 ready, and does not cover all known varieties, but it will 

 serve to convey a general idea of the leading lines along 

 which variation has developed : — 



Characteristic 

 Varieties. 

 Brachiatum. 

 Bamosum. 

 Cristatum. 

 Acrocladon. 

 DeltoideiDii. 

 Saytftatum (Scol.). 

 Trinerr'mm, (Blech.). 

 Anyustatum. 

 Bar/iesii (L. P. -mas). 

 Crispafum. 

 Comjesfuni. 

 Truncatum. 

 Peraferetis (Scol.). 

 FrizeUiee 



Victorife (A. F.-f.). 

 Mexuosiim, 

 Refle.tmn. 

 Revolvens. 

 Plumosum. 

 Grispum (Scol.). 

 Camhricum. (Polyp, v.). 

 Piilcherrimum. 

 Uotundatum. 

 Iiiterruptum. 

 Concinuum (Blech.). 

 Tripitinatum. 

 Divisilobum. 

 Cornubiense (Polyp, v.). 

 Projectum (Scol.). 

 Creiia t ii di ( Ceterach) . 

 JJiiricidinii. 

 Li Ilea re. 

 Siiprnlineatum. 



* Mr. Druery lias calculated that a well-developed Athi/rimn iti his 

 garden bears annually eleven hundred million spores. — British 

 Pteridological Society Report, 1896, p. 9. 



1. Alteration 

 of 

 skeleton 



2. Alteration 

 of 

 soft parts 



A. Branching 



B. Widening 



C. Narrowing 



D. Dwarfing 



E. Truncation 



F. Twisting 



G. Increase 

 H. Diminution 



I. Sub-division 



J. Murication 



Any scheme of this kind is unsatisfactory, for while 

 many varieties drop into their assigned places, as 

 many more belong to two or even three of the classes. 

 We shall now take each of the classes in turn, and 

 consider the range of its characteristics through the 

 various British Ferns, and some of its most remarkable 

 examples. 



A. — Branchino. — This is the best known and most 

 widely distributed of the abnormalities of Ferns, offering 

 a great variety of types and running to a greater or less 

 extent through every British species. The cause of this 

 tendency to branch in Ferns docs not ajipear to have been 

 sati8facU>rily explained. The branching is of various 

 types, of which four of the more freijuent are figured 

 diagrammatically below. Every gradation of branching and 



Fig. 1. — Types of Branching. 



2. Ramose. 3. Cristate. 4. Ramo-cristatc. 



cresting occurs, from tiny crestlets at the tips of the 

 ]iinu£e down to that exhibited by the extraordinary 

 Hart's-tongue known as glomerahim densnm Kelwayi, in 

 which by excessive branching each frond is reduced to a 

 dense hemispherical mass of parsley-like foliage a couple 

 of inches in height. This last-named form is further 

 remarkable for producing on its leafy surfaces innumerable 

 small buds, analagous to the bulbils borne by the Lesser 

 Celandine or Wood Onion, so that we may break a frond 

 into a hundred pieces and obtain fresh plants from every 

 one by half immersing it in soil. Branching in one 

 form or another has been found in many even of our most 

 refractory ferns — the Holly Fern, for instance, Lastrea 

 lemula, Asplenium Janceolatum, the Parsley Fern, Royal 

 Fern, and Beech Fern. The reader will remember {see 

 p. 116 supra) that the remarkable phenomenon of apospory 

 occurs in one of the densely crested varieties of the Lady 

 Fern, the tasselled tips of var. unco-glomemtum growing 

 out into prothallia if kept in a dam]i atmosphere. 



B. — Widening. — A class of varieties that need not 

 detain us. In some forms of Pulysfichum the frond 

 assumes a triangular outline, owing to the lengthening of 

 the lower pinnae. Other species exhibit an abnormal 

 development of the lowest pair only, thus approximating 

 to the brachiate form of branching figured above. A good 

 example of this is Blechnum Spicanf, var. trinerrium, 

 of which mention has already been made. Here the 

 increase of size is accompanied by a sub-division of the 

 enlarged pinnae. It is interesting to note that the un- 

 divided frond of the Hart's-tongue frequently exhibits 

 this character, the base projecting into two lobes, which 

 in a crested form may be themselves crested. 



C. — Nakbowino. — Not a common nor conspicuous form 

 of variation. One of the most pleasing Ferns in which it 

 appears is a triple variety of the male Fern, crispa crislata 

 angustata, the name of which sufficiently describes 

 its characters. 



D. — DwABFiNG. — The skeleton is sometimes dwarfed 



