16 POLYPOBIUM DRYOPTERIS, 



of fronds, that it must always remain one of the most beautiful 

 species of our cultivated Ferns. In a wild state it is an 

 inhabitant of mountainous rocky places, flourishing in shady 

 woods or beneath hedges, and although growing in damp 

 situations, it selects the driest places. The Oak Fern, or, as 

 it is sometimes called, the "Smooth Three-branched Polyj^ody," 

 is easily cultivated, requiring no care beyond the selection of 

 a proper place and suitable soil. It is very hardy, and readily 

 propagated by dividing the branching rhizoma. 



This species is a companion of the Beech Fern, and occurs 

 in the counties of Cheshire, Cumberland, Derbyshire, Durham, 

 Gloucestershire, Herefordshire, Lancashire, Northumberland, 

 Oxford, Shropshire, Somersetshire, Staffordshire, Westmoreland, 

 Worcestershire, and Yorkshire. In Scotland and Wales very 

 generally distributed. In Ireland exceedingly rare. 



A widely-spread European species, extending from Gibraltar 

 to the North Cape, and equally wide-spread in America, 

 extending from Columbia and Sitka to Labrador and Greenland. 

 A native also of the United States, Kamtschatka, Siberia, and 

 Africa. 



The fronds are pentangular-deltoid in form, three-branched, 

 the branches being stalked and triangular in shape. The two 

 basal branches less than the central branch, and narrower; 

 having also this distinction, — the terminal branch has the 

 pinna? equal in size on either side of the rachis, whilst in 

 the basal pair the branches are placed at an obtuse angle, 

 and the pinnte are much larger on the lower side of the 

 rachis. The fronds vary in size from four to twelve inches, 

 and are smooth, membranaceous, and brilliant green in colour. 

 The branches are pinnatifid above, and pinnate at the base. 

 The pinnge opposite each other, pinnatifid above, and pinnate 

 at the base, the apex being almost entire. Pinnules oblong 

 and crenate. Stipes smooth, frequently two or three times the 

 length of the rachis; erect in growth, slender, dark in colour, 

 and slightly scaly at the base. Rhizoma perennial, creeping, 

 branching, and dark coloured; roots black and fibrous. The 

 undeveloped fronds, when first growing, resemble three small 

 balls placed on slender wires. 



There is a flexuous mid-vein, with alternate veins to each 

 lobe, branching, and reaching the margin. 



