364 



I'roin which this fern is wholly absent ; and one of these spaces perhaps includes nearly 

 the whole of the Highlands. The Scolopendrium is reported to grow in the counties 

 of Renfrew, Lanark, Edinburgh, Forfar, Nairn and Orkney, and thus seems partially 

 to encircle the Highlands. But whether its extreme stations, or upper limits towards 

 the mountain centres, are found in these counties, remains to he shown. Again, Pte- 

 ris aquilina is exceedingly plentiful in Britain, from one extremity to the other, but 

 it fails upon the higher hills of Wales, the north of England, and the Scottish High- 

 lands ; and may even prove to be wholly absent from a transverse belt of high moors 

 and hills crossing Scotland about the 57th parallel of latitude. But what botanist can 

 trace on a map of Britain those portions of the surface from which this very conspicuous 

 fern is quite absent ? " — p. 103. 



" In returning from this digression respecting maps to the immediate subject of 

 the present paper, it may be farther observed, that ferns, as a class of plants, cannot 

 be exclusively connected with any particular local situation or quality of soil. For 

 the most part, a shady situation, damp ground and atmosphere, and a porous or peaty 

 soil, are suitable to ferns ; whilst exposure to sun, wind, and salt spray, as well as very 

 dry or marshy localities, are unsuitable. But some of the Asplenia grow in dry cre- 

 vices of rocks and walls, as also do Grammitis Ceterach, Polypodium Dryopteris, and 

 Polypodium calcareum, and even the less rigid ferns constituting the genus Cistopte- 

 ris. On the contrary, Osmunda regalis might almost be designated a marsh fern ; 

 and other species so far approximate to the same character, as to thrive in swampy 

 ground, that is, in watery places, where the soil is loose and spongy ; for example, 

 Aspidium Thelypteris. But ferns that grow well in swampy places will also grow 

 well on rocks and banks where the soil is not particularly wet ; for instance, Blechnum 

 boreale and Asplenium Filix-foemina. None are aquatics. One only is a littoral spe- 

 cies, Asplenium marinum ; and this one is occasionally seen in places many miles 

 from the sea. Osmunda regalis so frequently occurs near the shore, within reach 

 of the salt spray, and even at times within reach of high tides, that it might be regard- 

 ed as a sub-littoral species. None perhaps require the sun's rays directly shining upon 

 them ; but some few will bear daily exposure to the sun for several hours, though the 

 greater number thrive best on a slender allowance of sunshine. It cannot yet be stat- 

 ed that any species are absolutely limited to soils of a particular chemical or geognos- 

 tic character ; but Grammitis Ceterach, Polypodium calcareum, and the species of 

 Cistopteris, certainly affect lime rocks, though, indeed, it is believed by some bota- 

 nists, that the Polypodium calcareum is a variety of P. Dryopteris, varied in its habit 

 through the influence of soil or exposure. If so, the only species that is limited to 

 limestone, if even it be so limited, is Grammitis Ceterach. The harder kinds of trap 

 and slate rocks seem favourable to Asplenium septentrionale and Woodsia ilvensis. — 

 And, in general, the sand-stones are more productive of ferns than chalk or clays ; 

 though the difference here is probably owing more to the mechanical than to the che- 

 mical qualities of the soils." — p. 105. 



(To be continued). 



