In so large a group of plants as that pre sented by this family we must expect to find the greatest diversity of the and structure, depend ent on the geographical distribution, the altitu dinel distribution, and on the ecological condi tions under which the various members of the family have become developed. Marsh, swamp, rocky hillside, cliff and most ravine each have their characteristic species in every country, while the trees of every tropical region support an extensive epiphytic series which varies with every considerable change of altitude. Even ex posed cliffs in semi-arid regions support their own peculiar ferns, which have become adapted to conditions that at first would appear wholly unsuited to fern-growth. Obviously only a few of the more common species which grow wild or in cultivation can be mentioned here.
The sword-fern (Nephrolepis), some forms of which are known in cultivation as the °Bos ton Fern,* is a native of tropical America, oc curring frequently in peninsular Florida. In its native haunts it is more commonly found on the trunks of palm-trees, though it often grows on the ground or on rotten wood. It is a favorite in cultivation, either in hanging baskets or in jardinieres, and requires a rich soil and moist surroundings to thrive best. The son are provided with a kidney-shaped indusium.
The maidenhairs (Adiantum) are perhaps the most graceful of the herbaceous ferns. Over 60 species are known, many of which have long been in cultivation. The luxuriant split-leaved A. Farleyense and the numerous' fine-leaved varieties of A. cuneatum and A. gracillimum are among the most graceful in cultivation. Owing to their readiness to wilt most maidenhairs thrive best in Wardian cases.
In late years Japanese fern-balls have be come popular in cultivation, consisting of the slender rootstocks of a species of Davallia wrapped about a mass of peat-enclosed soil, and held in form by wires. The Davallias are graceful ferns mostly confined to the Old World, though related genera are found in the American tropics. Numerous species are found in cultivation in the larger conservatories. Among our wild species the ostrich-fern (Mat teuccia) is one of the best for out-of-door cultivation, to which it readily yields. It grows in graceful crowns from an erect rootstock, and has a bright green color. Its spore-bearing leaves are curiously rolled together so as to have the appearance of pods containing the copious sporangia. It requires a soil for its growth, and when growing wild thrives best in low ground. Other ferns suited for bed cultivation are the graceful wood-ferns (Dryopteris spinulosa, and related species) and the Christmas-fern (Polystichum), both with dark foliage and crown-like habit, and the hay fern (Dennstcedtia) with a foliage of lighter green and a more scattered habit of growth re sulting from its creeping rootstocks. The
wood-ferns and Christmas-fern are firm in texture, and remain green throughout the win ter; the hay-fern dies down with the early frosts. Another delicate pale-green species suitable for cultivation is the New York fern (Dryopteris Noveboracensis), which, however, has a range from New England to Alabama.
For rockeries the bladder-fern (Fills frag ilis), the smaller spleenworts (Asplenium tri chomanes and A. platyneuron), the rock-brake (Pellcea), and the curious walking-leaf are common among the best native species; and all thrive best if the rocks are part limestone. The last-named fern has a peculiar habit among our native species, shared, however, by many exotic ferns. The leaf, which is simple and tapers to a slender point from a rounded lobed base, takes root at the apex and forms a new plant, whose leaves may again take root and form still other plants. This peculiarity of taking steps away from the mother plant has given the name walking-leaf to this small fern, whose leaves range from 4 to 10 inches in length.
Aside from decorative value, ferns have lit tle utility. The matted tufts of soft hair-like scales of some of the Hawaiian tree-ferns (Cibotium) are collected in commercial quan tities and used for filling mattresses under the name '1)11110 The male-fern (Dryopteris filix mar) and some of its near allies are used in medicine as a vermifuge, and the soft parts of certain species are used for food. The mission of the fern, however, seems to be an msthetic one, to minister grace and beautify the duller and more prosaic sides of nature.
7. In point of grace and delicacy none of the ferns as ordinarily known can equal the filmies, which flourish best at the higher eleva tions of tropical lands. These ferns differ from the true ferns not only in the form of the sporangium, and its attachment to a thread like receptacle, but also in the texture of the leaf, whose blade is often only a single cell thick, so that the leaf is strongly translucent. The filmy ferns belong chiefly to the genera Trichomanes and Hymenophyllum, and although many are apparently so simple, the Hymeno phyllacece form one of the most highly differ entiated families among the ferns. A few others simulate them in texture, like the deli cate New Zealand species of Leptopteris and some species of Asplenium in the American tropics, but these are representatives of two distinct families. The genus Loxsoma repre sents a structural connecting-link between the genus Davallia and the filmy ferns, and this is apparently their only point of kinship. Two species of Trichomanes occur under moist rocks in some of our Gulf States, one of them scarcely over a half inch in height.