The best-known member of the genus, and the one having the greatest commercial value, is the common Hart's Tongue Fern (S. vulgare). The typical species is found growing wild in the copses and hedgebanks, and between rocks, in many parts of the British Islands, and is also distributed over North Africa, West Asia, Japan, and Northwest America. It has short stoutish rootstocks, and tufts of strap - shaped, bright - green leathery fronds 6 to 18 in. long. The "sori", or clusters of spore cases, are arranged in streaks almost at right angles to the midrib, but vary considerably in length and number. There are now almost innumerable varieties in cultivation, one hundred or more of which have been regarded as first-class garden plants by experts. The variations consist chiefly in the extraordinary way in which the simple fronds of the type have been modified into all kinds of shapes by cresting and laceration. Many of these varieties, it must be admitted, are mere vegetable monstrosities, curious rather than beautiful, but others are very ornamental in appearance.

Scolopendrium rhizophyllum.

Fig. 315. - Scolopendrium rhizophyllum.

The Hart's Tongue Ferns are now largely used for planting in moist and shady parts of the rock garden and flower border, or beneath overhanging trees and shrubs. They are all quite hardy, and flourish in sandy loam, peat, and leaf soil in about equal proportions. They are also excellent subjects for growing in cold greenhouses without any heat whatever.

A Frond with spore bearing spikes or cones (c), nat. size.

A Frond with spore-bearing spikes or cones (c), nat. size.

A very curious species is S. rhizophyllum, the "Walking Fern" of North America (fig. 315). The simple fronds taper to a point and have a pair of rounded auricles at the base, while new plantlets are developed at the tips of the fronds under favourable conditions. It is practically hardy in most parts of the kingdom.