26 BRITISH FERNS. 



side cliiefly the branching fibrous roots by which it clings to 

 its support. The fronds, if exposed to frost, perish ; but if 

 at all sheltered, they remain green during winter, and until 

 after young ones have been produced, which happens gene- 

 rally towards the end of May. The stipes, or stalk, of the 

 full-grown fronds is usually nearly equal in length to the 

 leafy portion ; the entire frond measuring from six to eigh- 

 teen inches in length. The leafy part of the frond is lance- 

 shaped in outline, but cut in from the margin along both 

 sides nearly as far as the midrib or rachis, and thus becomes 

 what is called pinnatifid. The portions into which it is di- 

 vided are called the lobes, or segments, or divisions of the 

 frond; and in this case they are usually oblong in form, 

 generally rounded at the end, but sometimes tapering to a 

 blunt point, and occasionally notched along the margin. 

 Each lobe has a slightly wavy midvein producing alternate 

 lateral veins (venules), which generally have about four vein- 

 lets or little veins disposed alternately ; it is the lowest of 

 these veinlets, on the side towards the point of the lobe, 

 which produces the sorus when it is present ; the rest, which 

 are barren, terminate in club-shaped heads, which are very 

 readily seen when a fresh frond is held between the eye and 

 a strong light. Most of the fronds of this kind of Fern pro- 

 duce fructification, which, however, is usually confined to 

 the upper half of the fronds, and has generally become ma- 

 ture by the end of September. 



It is an evergreen Fern, growing abundantly on pollard 

 trunks, mossy banks, moist rocks and walls, and old thatched 

 roofs ; and is pretty generally distributed over the United 

 Kingdom. It may be recognised by the comparatively large 

 circular patches of golden spore-cases ; no other native sort 

 having the fructification at all similar in appearance. 



The most remarkable variety is cambricum, commonly 

 called the Welsh Polypody, named Polypodium cambricum, 

 by Linnaeus. In this the lobes of the frond are broader, and, 

 instead of being simple, are deeply and irregularly lobed a 

 second time, the segments being rather sharply toothed. 

 This form, which is certainly only a variety of the common 

 Polypody, is always found without fructification. Under 

 slight shelter, where its fronds are persistent, it is one of the 

 most beautiful of what are called hardy Ferns. The Irish 

 Polypody, an equally elegant form, called semttacenim, is 

 found in Ireland and elsewhere ; in this the lower half of 

 the fronds are a second time lobed, and the upper half 

 usually fertile, and not twice-lobed. There is a form resem- 



