72 HISTORY OF BRITISH FERNS. 



fresh frond is held between the eye and a strong light. 

 Most of the fronds of this kind of Fern produce fructifica- 

 tion, which, however, is usually confined to the upper half 

 of the fronds, and has generally become mature by the end 

 of September. 



The most remarkable variety is cambricum, the Poly- 

 podium camhricum of Linneeus, commonly called the 

 Welsh Polypody. The lobes of the frond in this variety 

 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 semilacerum, is found in Ireland and else- 

 where ; the lower half of its fronds are a second time 

 lobed, and the upper half usually fertile, and not twice- 

 lobed. The variety omnilacerum is a fertile form re- 

 sembling camhricum, found in Herefordshire. These 

 three have a certain general resemblance. 



There are many other varieties which have been pro- 

 posed ; of which we may mention — bifidum, in which the 



