1 88 BRITISH FERNS 



THE POLYSTICHUMS (The Shield Ferns) 



The genus Polystichum is represented in this country by three 

 species, viz. P aculeatum, the Hard Shield Fern, P. angular e, the 

 Soft Shield Fern, and P. lonchitis, the Holly Fern, all of which are 

 similarly characterized by the peculiar form of the ultimate sub- 

 divisions, which are shaped somewhat like a fingerless glove, the 

 thumb projecting at nearly right angles. Their edges are, however, 

 sharply toothed and their terminals sharply pointed. This pecu- 

 liarity is clearly seen in many of our illustrations, but, as will also 

 be seen, especially in the case of P. angulare, the make of the 

 frond and subdivision varies very greatly, so that sometimes it is 

 both marked by partial suppression, or accentuated by lengthening 

 of the segments. All three species are perfectly evergreen and hardy, 

 and a further peculiarity by which they may be recognized, when 

 the fronds are rising and unfolding in the spring, is that as the 

 terminal coil develops and loosens, it falls over backwards, and 

 hangs like a reversed crozier, an exception to the general rule. At 

 this stage, too, the protecting scales, which are plentiful, are snow- 

 white, only eventually becoming brown. The spore heaps of this 

 genus are perfectly round, and are covered by a circular indusium, 

 attached mushroom fashion by a short central stalk. This, having 

 a resemblance to a shield, gives the popular name to the genus. The 

 fronds are deep green, and with a shining surface, especially in 

 P. lonchitis and P- aculeatum ; their distinguishing characters, 

 however, will be treated of under their respective names. All three 

 species have yielded varieties, P. lonchitis a few, and P. aculeatum 

 a fair number, but P. angulare has been far and away more generous, 

 and ranks, indeed, with the four or five most versatile Ferns we 

 possess. With these few introductory words we will now proceed 

 to treat of them individually. 



Polystichum Aculeatum (The Hard Prickly Shield Fern) 



(Plate XXVII) 



Polystichum aculeatum, or the Hard Prickly Shield Fern, is 

 intermediate in texture between P. lonchitis, the Holly Fern of the 



Fig. 213. P. aculeatum (pinna 



mountains, and P. angulare, the Soft Shield Fern of our warm' 

 lowland districts, and is also to some extent intermediate in its 



