THE POLYPODIES 



169 



Fern, but with a less delicate shade of green, while its developing 

 fronds (Fig. 190) do not divide at the outset into three ball-like 

 pendants, but form a crozier-shaped pendulous hook. It imitates 



Fig. 190. P. calcareum (pinna). 



the Oak and Beech Ferns exactly as regards its creeping rootstocks 

 and general habit of growth, but differs from them in its confine- 

 ment, as its name indicates, to limestone soils, which, under culture, 

 necessitates an admixture of old mortar, chalk, or other form of 

 lime, in the station assigned to it. Treated thus, it is equally 

 easy to grow. It has yielded no varieties. 



Polypodium Dryopteris (The Oak Fern) 



(Plate XXIV) 



This most beautiful little Fern, whose name is equally difficult 

 to explain as that of the Beech Fern, and for the same reason, 

 differs markedly in the make of its fronds from P. phegopteris, 

 these being triangular in outline, and practically consisting of three 

 branches, each of which is again triangular and pinnate. The 



P. dryopteris (pinna). 



stalks are long and very slender, and the leafy portion of the frond 

 is bent backwards at an angle at the junction of stalk and frond, 

 the fronds (Fig. 191) thus spreading more or less horizontally. 

 A curious feature in this species is that when the fronds commence 

 to unfold, the three divisions loosen and fall apart in the shape of 

 three round balls, exactly like a pawnbroker's sign. Another dis- 

 tinctive feature is the peculiarly delicate moonlight green of the 

 fronds, which, and its general habit, render it one of the prettiest 

 of our native Ferns. Its usual height is six to eight inches. As 

 regards its habitats and cultural requirements, they are precisely 

 those of the Beech Fern, and need not, therefore, be repeated. 



