How to Know the Ferns

by S. Leonard Bastin

Asplenium ruta-muraria. The Rue-leaved Spleenwort.

A very charming little species, with which most people who take the least interest in Ferns are probably familiar. In reality this plant is a rock Fern, but it often finds a congenial home on old walls. The Wall Rue has a tufted root-stock which is furnished with a quantity of fibrous roots; these often force their way for a considerable distance into the crevices. From the root-stock arise a number of little fronds; where the situation is dry, and the battle for existence is a hard one, these may not be more than a couple of inches in length. In damp situations the fronds might measure three times as much. Where the examples are dwarfed the stipes will be about the same length as the leafy portion, but in a well-developed instance it will be much longer. The colour of the fronds is of a dark green colour, and these are of a somewhat leathery nature. In a fair-sized example the frond is twice pinnate, the pinnæ are definitely stalked, and the pinnules are roughly wedge-shaped, being somewhat toothed at the lip. The Wall Rue is excessively variable, and in exposed places it is possible to find plants bearing fronds which are only divided once, the pinnæ being segmented.

Back of frond of Asplenium ruta-muraria. Enlarged.

The sori are in the form of lines which branch out from the lower part of the pinnule in a fan-shaped manner. The indusium disappears as soon as the sporangia become mature, and eventually the sori may spread over the whole of the back of the pinna or pinnule.

The Wall Rue is really a very common Fern, but it is often overlooked when hiding in the dark crevice of some old wall. The plant has a wonderful habit of adapting itself to dry conditions. It is of easy cultivation if it can be given an open and well-drained situation. The Wall Rue is an evergreen plant.

Asplenium adiantum-nigrum. In this case the specific name is formed of two words, the first of which belongs to the true Maidenhair Fern. As has already been explained, it comes from a Greek word which means “unwetted,” a reference to the fact that the fronds do not become damp when it rains. The word nigrum, of course, simply means black, and is obviously an allusion to the colour of the leaf-stalks of this Fern. The Black Maidenhair Spleenwort.

A very pretty Fern, which in some ways is to be regarded as the most attractive of all the Spleenworts. The species varies a good deal according to the situation in which it is growing. Thus in dry hedge-banks it will be a comparatively small Fern, whilst when growing in damper situations—such as by the side of a waterfall—it will be very much larger. The root-stock is thick and is densely covered with scales, and from it arise the leaf-stalks, which are black towards the base. The stipes is usually about the same length as the leafy portion. In the varying forms the fronds range from about four inches to a foot, or even more, in length. In the smaller examples the fronds are twice pinnate, whilst the larger leaves may be thrice pinnate. The general outline of the frond is triangular, and the pinnæ, which are arranged alternately on either side of the rachis, are somewhat similar in outline. The pinnules are shaped like wedges and have toothed lobes.

If we turn up a frond of the Black Maidenhair Spleenwort we shall discover the sori situated on veins which issue from the mid-veins of the pinnules. In their early days these clusters are distinctly in the form of lines, but after the throwing off of the indusia they rapidly mature and spread to such an extent that the whole of the under-surface of the pinnule is covered. Often an entire frond appears to be completely brown on its underside.