POLYPODIUM. 



131 



in Wedwood Forest, near Yoxhall Lodge, Staffordshire ; at High CliiF, 

 Cheshire ; at Boghart Hole Clough and Prestwich Clough, in Lancashire ; in 

 Barrowfield Wood, near Kendal ; near Durham ; in Leigh Woods, near Bristol ; 

 on Frocester Hill, G-loucestershire ; among rocks at the Fall of Lodore, 

 Derwentwater, in Cumberland ; above Langley Ford, near the Cheviot 

 Mountains, and in many other places ; but invariably in perfectly cool, sheltered, 

 moist spots where the temperature is subjected to very little variation during 

 the summer. 



Of the four native species of Polypodies with deciduous foliage, P. 

 Dryopteris (or, as it is popularly called, " Oak Fern," for which appellation 

 there is no reason, unless it be that it is so named from being frequently found 

 among the moss about the roots of 

 Oak-trees) is undoubtedly the one 

 most generally known and most de- 

 servedly appreciated. On account of 

 the peculiarly bright pea -green colour 

 of its fronds, and of its close and 

 compact habit, it is much admired 

 and frequently used for forming in 

 the hardy Fernery edges which, all 

 through the summer, possess a fresh- 

 ness looked for in vain among all 

 other Ferns of dwarf habit. These 

 fronds, produced from a wide-creeping 

 rhizome of a very slender nature, and 

 borne on slender stalks 6in. to 12in. 

 long, naked upwards and slightly scaly below, are deltoid (in shape of the 

 Greek delta. A) and generally measure from 6in. to lOin. each way. Their 

 lower leaflets are much the largest (Fig. 41), and the spear-shaped pinnules 

 (leafits) are slightly notched. They are of a soft, papery texture and smooth 

 on both surfaces. The abundant but minute sori (spore masses), of a light 

 brown colour, are scattered over the whole under-side of the frond. A 

 peculiarity noticeable in this species consists in the development of the fronds, 

 the rolled-up leaflets of which, in a young state, resemble three small balls 

 or green peas placed on wires. — Hooker, Species Filicum, iv., p. 250 ; British 



K 2 



Fig. 41. Polypodium Dryopteris 



(much reduced). 



