PERNS OP GREAT BRITAIN. 21 



thatch, or on stone wall or rugged rock. The frond varies 

 from a few inches to a foot and a half in length, and 

 attains its full expansion earlier than most of our native 

 Ferns, being usually developed by the month of May. 

 If in a sheltered spot, it retains its verdure till December, 

 but on an exposed situation, it is easily destroyed by 

 frosts. The leaves have a faint and rather disagreeable 

 odour, and, if tasted, leave a rough and unpleasant feel- 

 ing on the tongue. Several foreign species of Polypody 

 are, however, aromatic, and the fronds of some are used 

 by the natives of the Sandwich Islands to give a per- 

 fume to the cocoa-nut oil with which they anoint them- 

 selves. The roots of our common species are very 

 numerous, forming entangled masses, and the horizontal 

 underground stems are entirely covered, when young, 

 with pale brown scales, which disappear as the plant 

 becomes older. The slender stalk of the frond rises 

 from this brown creeping stem, and is usually clothed 

 rather more than half-way down with the leafy portion. 

 This is lanceolate, and divided into lobes, almost to its 

 midrib. The lobes are usually oblong, and rounded 

 at the end, but in some specimens they taper to a 

 point. The margin is generally entire, but is sometimes 

 slightly serrated. A mid-vein winds through each lobe, 

 and lateral veins are produced alternately from it. The 

 same alternate disposition is to be seen in the veins 

 arising from these, which are generally four in number, 

 and it is usually on the lowest of these branches that 

 the large, round, bright orange-coloured clusters are 

 seated; the remaining veins, which are barren, have 

 httle club-shaped extremities. The fructification is very 



