when shaken straight out of the cones it does not always ignite very readily. One of the Horsetails, the Dutch Rush (Equisetum hyemale), was—and perhaps is still—used in polishing, owing to the large amount of silica which is present in its stems. In addition, those who are interested in coast erosion say that the stronger-growing species of Equisetum should be planted to keep clay cliffs from falling. From an ornamental point of view the Ferns and some of the Club Mosses are, of course, of great value. They are widely cultivated in garden and greenhouse, and we may say that these plants make up in æsthetic value what they lack from an economic point of view.

CHAPTER IV
THREE DAINTY FERNS

Although the members of the family Hymenophyllaceæ are largely tropical, we are fortunate in having three representatives in the United Kingdom. Two of these, both Filmy Ferns, are not so familiar to people as they might be, if folk were only a little more observant; whilst the Bristle Fern is only to be found in the South of Ireland. All the species require an abundance of moisture, and they attain their greatest perfection on rocks which are dripping with water.

Trichomanes radicans. The generic name is said to be derived from two Greek words—thrix, “a hair,” and manos, “soft”; the specific name is obviously connected with the Latin radix, “a root,” and has reference to the creeping rhizome. The Bristle Fern.