- 


188 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. angulare, 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 
Бе seen, especially in the case of P. angulare, the make ої Ше 
frond and subdivision varies very greatly, so that sometimes it is 
both marked by partial suppression, or accentuated by lengthening 
of the segments. Al 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) 
Е (Plate ХХУП) 
Polystichum aculeatum, or the Hard Prickly Shield Fern, is 
intermediate in texture between P. lonchitis, the Holly Fern of the 

Fig. 213. 2. aculeatum (pinna). 
mountains, and P. angulare, the Soft Shield Fern of our warm 
lowland districts, and is also to some extent intermediate in its 


