THE MARSH BUCKLER FERN. 1 13 



Aberdeen, Argyle, Ayr, Berwick, Caithness, Clack- 

 mannan, Dumbarton, Dumfries, Edinburgh, Elgin, Fife, 

 Forfar, Inverness, Kincardine, Kinross, Lanark, Perth, 

 Renfrew, Ross, Roxburgh, Stirling, and Sutherland ; 

 also in the isles of Arran, Cantyre, Islay, Shetland, and 

 Uist. In Ireland, in the counties of Clare, Donegal, 

 Galway, Kerry, Londonderry, Waterford, and Wicklow. 

 It is found growing at various altitudes up to three 

 thousand feet above the sea-level. 



XXXVII. THE MARSH BUCKLER FERN. 



Lastrea thelypteris. 

 (Plate X., Fig. r, page 67.) 



LENGTH OF FROND. Barren fronds, one foot to three 

 feet ; fertile fronds, a foot to four feet. 



GENERAL DESCRIPTION. Roots black, fibrous, abun- 

 dant. Rootstock, an extensively-creeping rhizoma, slender 

 and blackish. Fronds of two kinds barren and fertile 

 numerous, light green, herbaceous, brittle, fragile ; 

 stipes about equal to the leafy part, very thin, pale green, 

 delicate, and brittle ; leafy part lance-shaped, broadest in 

 the centre, tapering to a somewhat blunt point at the 

 apex, and tapering slightly towards the base ; pinnae 

 opposite or alternate, and somewhat distant along the 

 rachis, long, narrow, pointed, broadest at the base, 

 pinnatifid each pinna deeply cleft into thin, plain, 

 oblong, entire pinnules. The pinnules of the fertile 

 fronds, besides being longer, are somewhat more con- 

 tracted than those of the barren ones. Fructification 

 borne in rows of sori upon the under sides of the pinnules, 

 midway between their midveins and their margins, each 

 sorus roundish in shape and covered by a roundish 

 indusium, which, however, soon falls off and disappears. 



