How to Know the Ferns

by S. Leonard Bastin

Polystichum lonchitis. The Holly Fern.

The Holly Fern, as indeed are all the species of Polystichum, is very distinct from a Nephrodium in the matter of its indusium. This is quite circular, and has no notch; moreover, it is attached to the pinnules by a short stalk in the centre. Thus it is proper to describe the shape of the indusium as peltate. The sori are chiefly confined to the upper portion of the back of the frond, and are situated on either side of the midrib of the pinnæ. After the falling away of the indusia the sori tend to spread, so that they may finally cover almost the whole of the back of the fertile pinnæ.

The Holly Fern is essentially a plant of the mountains, and it is often found growing in the most exposed situations. It is not common in England, though it has been found in a few localities in the north. The species has a much wider distribution in Scotland. The Holly Fern is evergreen in habit, and its stiff fronds seem to be able to withstand the severest frost. The plant is rather a difficult one to grow, though if it can be given a rock crevice it will sometimes settle down happily in the garden. The foliage of the Holly Fern lasts through the year.

Polystichum (Aspidium) aculeatum. In this case the specific name is a Latin term simply meaning “provided with prickles”—an allusion to the fact that the fronds are adorned with spines. The Hard Prickly Shield Fern.

This species is very distinct in its general appearance from the Holly Fern, though it can at once be seen to be a Shield Fern by the unnotched indusia which cover the sori. The fronds may be as much as two feet in height, or even a little more, and these rise from a tufted root-stock. As a rule the stipes is very much shorter than the leafy portion, and both it and the rachis are thickly covered with scales. The outline of the frond is lanceolate, and the colour of the foliage is dark green. A pretty glossy effect is noticeable on the upper surface. The frond of the Hard Prickly Shield Fern is twice divided, and the pinnæ are arranged alternately on either side of the rachis. A distinctive point about this species is that the upper pinnules at the base of each pinna is larger in all ways than the other pinnules. The pinnules are provided with sharp teeth, and it should be noted that they have nothing very decided in the way of stalks. Actually they are what botanists call decurrent—that is, tending to run together at the base. In some varieties of this species the tendency is more marked than in others.

The sori are placed on either side of the mid-veins of the pinnules, and these are usually confined to about half the upper portion of the back of the frond.

The Hard Prickly Shield Fern is very widely distributed in England, and it is to be looked for in shady woods. It is an exceedingly easy plant to grow, and thrives even in town gardens. The plant is evergreen in habit.

Polystichum (Aspidium) angulare. It is not regarded by some botanists as an established species, but is thought to be a variety of A. aculeatum. However, there are certain differences which appear to be specific. The Soft Prickly Shield Fern.

As in the Hard Prickly Shield Fern, we find a tufted root-stock from which grow lanceolate fronds. We notice the same short stipes and the narrow pinnæ on the leafy portion tapering to a point. In this species it is said that the pinnules at the base are more nearly equal in size than is the case with A. aculeatum. The pinnules are also more definitely stalked in the former than in the latter. In the case of the Soft Prickly Shield Fern, it is noticeable that all parts of the stalk of the frond—both stipes and rachis, and even the rachides—are covered with brown scales. It is said, too, that the droop of the fronds is more pronounced in the Soft Prickly Shield Fern than in the Hard Prickly Shield Fern.