FERN TRIBE 141 
the mid-rib on its upper surface. The length of a full-grown frond is from 
six to thirty inches. It grows very luxuriantly on stone walls, at the borders 
of streams, or the sides of wells, and is sometimes found in mines or caverns. 
It is by no means a mountain fern, for it is not known at greater elevations 
than about 600 feet. 
Sir J. E. Smith says of its fronds: ‘In the now open vault by the great 
hall in Conway Castle, I have gathered them upwards of three feet long, 
and nearly five inches wide.” Sir W. J. Hooker found them in the moat 
at Kenilworth Castle more than two feet long. A very stout and strong 
mid-rib runs through the leafy part, from which forked veins arise, the 
smaller veins being parallel to each other, and running towards the margin, 
but ending just within it. Oblong clusters of fructification, some long 
and some short, lie in the direction of the veins, at short intervals, on the 
upper part of the leaf, occupying about two-thirds of its length. They 
are placed in oblique parallel lines on each side of the mid-vein, and when 
seen in their ripened state appear to be single. If these are examined when 
young, they may, however, be seen to be composed of two distinct patches, 
facing each other, and divided by a small line, which is finally hidden by 
their uniting into one mass. Each of the lines consists of a complete cluster, 
and when joined together this is called a twin-sorus. This twin-sorus is 
always placed between two bundles of veins, and covered by the thin white 
membrane-like indusium of the same formas the clusters. In an early stage, 
the indusia, touching each other, seem like one only; then they separate 
slightly, the distinction between them becoming daily more apparent, till 
they finally become widely separated and fall off. 
This plant was considered of some medicinal use by our forefathers, and 
was included in what were termed the five “capillary herbs.” The golden or 
common polypody, the common maidenhair, the common spleenwort, the 
wallrue, and Hart’s-tongue, formed this group, which was in early days 
held in great esteem. 
The Hart’s-tongue offers an enormous number of ee eee especially 
when cultivated, as it so often is, on rockwork. A very elegant and common 
variety, termed crispwm, is so waved and curled at the margin, that it becomes 
a leafy frill on each side of the mid-rib ; it is often of a much paler green 
than the common form of the Hart’s-tongue. Another well-known variety 
is that termed polyschides, in which the frond is narrow, linear, deeply and 
irregularly cut at the margin into roundish lobes. A third variety, lobitum, 
has its fronds strap-shaped below, widening at the upper part, and there cut 
into two or more acute lobes ; and a very beautiful variety, mulizfidum, has 
its fronds strap-shaped below, spread out at the upper part, and cut into 
crowded, more or less blunt, and wavy lobes. A fourth variety is very 
remarkable, and has been found on a wall near Taunton and at Strabane ; 
it is termed lacerdtum, and has its broad fronds deeply lobed or pinnatifid. 
The cultivated varieties are well-nigh endless, and some of them are very 
remarkable. 
Some forms of this fern are found, when under culture, to be viviparous : 
that is, buds arise upon the stem, which separate spontaneously from the 
plant itself, and become young ferns. A variety of Polystichum angulire 
