360 



again are either confined to a few localities, or have a wide range 

 over certain parts of the island although excluded from others. 



A table is next given wherein are enumerated fortj-three species, 

 showing in how many of the twenty local Floras before mentioned, 

 and in what number of twenty-four manuscript lists, the name of 

 each species occurs. By this means may be gained a tolerably cor- 

 rect idea of the range of our native ferns ; although, as the author ob- 

 serv^es, " without regard to the distinctness of the species, the dates of 

 their first discovery, and the certainty of their nomenclature," errone- 

 ous conclusions might be drawn from the list. 



Pteris aquilina, Polypodium vulgare and Aspidium Filix-mas are 

 the only three species " so universally distributed as to be included in 

 all the forty-four district Floras and lists." But although these are 

 our three commonest ferns, yet to neither of them does the widest ge- 

 ographical range in Britain belong. " The most widely ranging of 

 our native ferns, taking into view the three directions of latitude, lon- 

 gitude and elevation, are Blechnum boreale and Aspidium dilatatum 

 (or spinulosum)." 



" It has been already stated that ferns prevail chiefly in the hilly tracts towards the 

 north and west, and that they are less numerous in the low south-eastern counties of 

 England, — a peculiarity that is doubtless in great measure attributable to the more 

 humid and cooler atmosphere of the former. The three circumstances on which this 

 difference of climate depends, are those of latitude and longitude, conjointly with ele- 

 vation of the surface ; and the influence of these three conditions in producing the ge- 

 neral result, will scarcely admit of divided consideration. We may, indeed, trace some 

 agreement betwixt the range of certain species and the geographical divisions of lati- 

 tude and longitude ; yet this connexion (or, more strictly, this coincidence) is so much 

 interfered with by the third condition, that of height, as to render separate investiga- 

 tion almost useless." — p. 97. 



In proof of these positions it is remarked that about half the num- 

 ber of indigenous ferns are absent from the English counties lying to 

 the east of Gloucestershire and Nottinghamshire ; " whilst none of the 

 species found growing in these south-eastern counties are wholly want- 

 ing in those to the westward of them ; most of these species also being 

 much more plentiful in the western counties." The paucity of ferns 

 in the south-eastern counties is accounted for by the different cha- 

 racter of the surface, owing to the absence of rocky ravines, waterfalls 

 and mountain elevations, and the consequent dryness of atmosphere, 

 rather than by the difference of longitude. 



Nor is the northern or southern limit of a fern's range altogether 

 to be determined by the degree of latitude, though they may be more 



