87. FILICES. 285 



Native. Ericetal. One of the few ferns that thrive as 

 well or better in open and exposed situations, while the 

 great majority are more particularly adajDted to the shade 

 of woods, or to the more partial shelter of steej) banks 

 and rocks ; in which respect this fern is allied to Pteris 

 and Allosorns, as it is also to the latter by the differences 

 of barren and fertile fronds. If wholly absent from Hunt- 

 ingdon or Buckingham, for which I have no authority to 

 cite, the comital estimate must be kept below 82. Eleven 

 other counties, for which I am equally unprepared to cite 

 authorities, are so extremely probable as to be all unhesi- 

 tatingly reckoned in the estimate. Taking both horizontal 

 and vertical range into account, this is perhaps the most 

 widely distributed of aU our ferns ; Lastrea dilatata being 

 its nearest ally or rival in this respect. 



1404. Pteris aquilina, Linn. 



Area general. 



South limit in Cornwall, Isle of Wight, Kent. 



North limit in Shetland, Orkney, Hebrides. 



Estimate of provinces 18. Estimate of counties 82. 



Latitude 50 — 61. British tj^e of distribution. 



Agrarian region. Inferagrarian — Superagi-arian zones. 



Descends to the coast level, in the Peninsula. 



Ascends nearly to 650 yards, in East Highlands. 



Range of mean annual temperatui-e 52 — 40. 



Native. Ericetal, Sylvestral. Some remarks on the 

 altitude attained by this fern in Scotland, have been be- 

 fore given (vol. i. pp. 33 — 4). Actually, its upper Hne, 

 traced on the acclivites of the mountains, exceeds that of 

 cultivation in some places ; and thus, if measured by the 

 test of cultivation strictly, the Pteris should be considered 



