B. Leptosporangiata.— The ferns proper, including nearly 4,000 species, are divided un equally among the eight families of this sub class. They are leptosporangiate (that is, the sporangia develop from the epidermal tissues), and all produce green prothalli of the type de scribed above. Except the Matoniacets, a small family of two species, all are represented in America. Two families are tropical only, while the remaining five are also represented in the United States.
1. The flowering ferns, so called because the sporangia are panicled, are among the conspic uous features of our northern swamp vegeta tion in spring and early summer. The cinna mon-fern grows in great crowns, sending up its spore-producing leaves, which have a rich cin namon color, a short time in advance of its rich crown of foliage-leaves. The royal flow ering-fern grows in similar locations, but is larger, has more compound foliage, and bears its panicle at the summit of the foliage-leaf. The flowering ferns (Osmunda), with two genera from New Zealand and Africa, make up the family Osmundaceee with 16 species. In this family the ring of the sporangia is rudi mentary and the sporangia opens longitudinally.
2. The Hartford fern or climbing fern (Lygodium) is the type of a second small family. Our species is low-growing, only two or three feet high, and twines closely about other vegetation. It is quite local, but where it grows it sometimes forms tangles. In Connec ticut it is so rare that it is protected by law. The tropical species of this genus often climb trees for 40 feet or more. Another member of the same family is the curious curly-grass (Schiscea) of the pine-barrens of New Jersey. It is wholly unlike ordinary ferns, the foliage leaves resembling curled grass-leaves and the spore-bearing leaf resembling a small sedge. The entire plant is only four or five inches high. These two species with two subtropical species of Ornithoptens form our four representatives of the family Schisceacece, whose 80 species are largely South American, though several species occur in the Old World. They are character ized by their pear-shaped sporangia with an apical ring. The sporangia are usually borne in spikes or panicles.
3. The Gleicheniacece are found in the trop ics of both hemispheres, several species of Dsc ranopteris occurring in the uplands of the West Indies, forming almost impassable tangles or thickets. These ferns, instead of uncoiling at once, produce buds in the axils of the forked branches, and as the lower portions mature these buds develop successive upper growths. The tangles thus formed are often sufficient to bear the weight of a man, and it is possible to walk for some distance on these thickets.
4. The floating-fern (Ceratopteris), found rarely in Florida and Louisiana, and occasion ally throughout the tropics of both hemispheres, is almost the only aquatic representative of the order. Its sterile leaves float on the surface of
shallow waters, and its pad-like fertile ones project above the surface. The name Ceratop tens is derived from this fertile leaf, which branches like a deer's horn, and gives the name to the family Ceratoptendacem 5. The tree-ferns of both hemispheres form a separate family Cyatheacece, though several members of this family are very diminutive, and ferns with trunks occur occasionally in other families. No tree-ferns occur in the United States, but 30 species or more are found in the higher altitudes of the West Indies, and many more occur in other tropical regions. In some portions of the mountains of Jamaica tree-ferns form half or three-fifths of the for est vegetation the trunks ranging from 6 to 50 feet in height. A well-developed tree-fern forms one o the most beautiful types of vege tation, rivaling the palms in grace and perfec tion of form. Some 200 species have been de scribed, belonging chiefly to the genera Cya thea, Alsophda, Hemitelia, Dicksonia and Cibotium.
6. The great mass of our ferns belong the to the ce family Polypadiace, often known as h true ferns, perhaps for no better reason than that they were the first to be called by the name of ferns. The members of this family have defi nitely stalked sporangia, always provided with an elastic vertical ring which causes the sporan gium to burst transversely and thus disperses the spores. In some species, like the stag-horn fern, the sporangia are spread over the under leaf surface in a uniform layer; in others, like the spleenworts and bird's-nest fern, they are in definite lines; while in our common poly pody, the maidenhair, and the wood ferns they are in small rounded masses (sori). In some species the sorus is naked, but in most it is covered by a small membrane (indusium), pri marily for the purpose of protecting the young sporangia. In some ferns, like the spleenworts, the indusium develops along a vein; in others, like the Christmas-fern, it is attached at one point and covers the sorus like an umbrella; in still others, like the maidenhair, it is formed of a modified portion of the margin of the leaf folded under so as to cover the young sporan gium. The nature and position of the indusial covering forms one of the leading characters for the separation of genera under the Hook erian scheme of classification, while the Pres lian scheme lays stress on the character of the venation, the fundamental branching of the fibro-vascular system of the plant. A more rational and natural scheme combines with these the habitual and biological characters that serve to group in each genus ferns that really have a natural relation to one another.