144 ENGLISH BOTANY. 



acute, with the margins revolute, each with a central mid-vein, which 

 gives off venules which anastomose so as to form a flexuose vein on each 

 side of the mid- vein and parallel to it, between which and the margins 

 of the segments the venules are free. Rachis purplish-brown. Sori 

 linear, attached to the longitudinal vein formed by the anastomoses 

 of the venules, covering the whole under surface of the segments 

 except the apex. Indusium linear, continuous. Spores faintly tuber- 

 culate, with a few small blunt tubercles. 



On heaths, hedgebanks, and woods, common and generally distri- 

 buted, except in chalky or limestone districts. 



England, Scotland, Ireland. Perennial. Autumn. 



Barren fronds, including the stipes, 6 inches to 2 feet long, but 

 most commonly 12 to 15 inches by 1 to 2 inches broad or more ; 

 fertile fronds 1 to 3 feet high rising from the centre of the spreading 

 sterile fronds. Like Scolopendrium vulgare, the present species 

 produces numerous monstrous forms much prized by fern-growers. 

 Most of these variations take place in the barren frond, although in 

 some cases the fertile frond is also divided. 



Hurd Fern. 



Tribe VI— PTERID.E. 



Rootstock velvety, extensively creeping, growing in advance of 

 the fronds, the stipes of which is not articulated to the rootstock and 

 does not separate from it. Sori marginal, linear, straight, continuous, 

 attached to a vein which is parallel to the midrib and margin of the 

 frond or segment, which is reflexed over the sorus, and has the 

 margins cut into capillary segments, forming an accessory indusium ; 

 true indusium attached to the vein within the sorus, membranous, 

 fringed. 



GENUS XVII.— P T E R I S. Linn. 



Rhizome velvety, growing in advance of the fronds. Fronds soli- 

 tary, decompound, their stipes not articulated to the rootstock and 

 not separating from it. Veins not anastomosing, but having their 

 apices connected by a marginal vein. Sori marginal, linear, straight, 

 continuous, attached to a vein which is parallel to the reflexed margin, 

 lying between two membranes of which the inner one is the smaller 

 and sometimes absent, though it is probable that it represents the 



