FERNS (ante), a group of cryptogamous or flowerless plants, much prized for their beauty, of which more than 2,500 species have been described by botanists. They formed a prominent feature in the vegetation of the early geological ages, and are found at present in every quarter of the globe, being comparatively few and small in cold climates and large and abundant in the tropics. They grow from a woody stem that first creeps along or under the ground, then becomes erect, and sends forth from the sides, or at the top, leaves or fronds of varied and most curious patterns. They vary in size in different climates, from herbaceous perennial plants with a slight stem pro ducing leaves often less than half an inch in length, to trees rising in the tropics to a height of from 50 to 60 ft., and sending out at the top a beautiful crown of fronds from 8 to 20 ft. in length. Ferns are fructified from the lower face or the edges of the fronds, on which are collections of capsules filled with seeds or spores. A spore on ger mination produces a structure which, compared with its immediate parent, is very small, and bears no resemblance to it in form or texture. It is called the prothallium, and its function is entirely reproductive; it develops sexual organs of two kinds, archegonia and antheridia, either on the same or different prothalia. Hence, in contradistinction
to the sporophore—the function of which in this group of plants is purely vegetative— the prothalial generation is termed the oophore. The whole group of ferns (pterido phyta) has been classed as follows: PrEuruorurrA.—Cormophyta with two distinct stages in the life-cycle. Sporo phore with high vegetative differentiation. Oophore inconspicuous and destitute of vascular tissue.
Class I. Filicino3.—Leaves highly developed. Sporangia numerous on the fertile leaves.
Sub-class 1. Filkes.—Leaves without stipular appendages. Sporangia epider mal, containing spores of one kind developed in each from a single primary mother-cell.
Sub-class 2. Stipulalce. —Leaves with stipula-like appendages. Sporangia con taining spores of one kind developed in each from many endogenous pri mary mother-cells.
Class II. Equisetineo3.—Leaves rudimentary. Sporangia 5 to 10 on the fertile leaves. Class III. Lycopodince. —Leaves small (except isoetes), simple. Sporangia solitary. Sub-class 1. Lycopodiaccce.—Spores of one kind.
Sub-class 2. Ligulata—Spores of two kinds.