THE RIGID BUCKLER FERN 49 



The stipes is densely scaly. The venation is similar 

 to that of Filix-mas, the pinnules having a flexuous 

 midvein, with alternate venules again pinnately 

 branched. The sori are borne on the lowest anterior 

 branch of each venule, that is, on the lowest veinlet on 

 the side next the apex of the pinnule, and are covered 

 by a kidney-shaped indusium which does not fall away. 



The Eigid Buckler Fern is almost entirely confined 

 to a few limestone craggy tracts within a small area of 

 the contiguous parts of Westmorland, Lancashire, and 

 Yorkshire. The Eev. GK Finder writes:"! met 

 with Lastrea rigida in great profusion along the whole 

 of the great scar limestone district, at intervals be- 

 tween Arnside Knott (where it is comparatively scarce) 

 and Ingleborough, being most abundant on Hutton 

 Roof Crags and Farleton Knott, where it grows in the 

 deep fissures of the natural platform, and occasionally 

 high in the clefts of the rocks ; it is generally much 

 shattered by the winds, or cropped by the sheep, which 

 seem fond of it. With regard to the shape of the 

 frond, I may mention that among some hundreds of 

 specimens I found but one or two which had the fronds 

 oblong-lanceolate, all being more or less triangular, and 

 not having the lower pair of pinnse shorter than those 

 in the upper and middle parts of the fronds. The 

 fronds of young plants are remarkably triangular. 

 The two forms of fronds no doubt depend upon the 

 situation, whether sheltered or otherwise, and on other 

 causes ; still I imagine the triangular to be the true 

 Form of the plant." Its elevation above the sea ap- 

 pears to range between 200 and 1,500 feet. In 

 1 



