The Cyatheineæ are chiefly arborescent ferns, and, with the exception of some fossil species, contain the noblest representatives of the cryptogamic flora. Their fructification consists of dot-like sori, in which the usually compressed oblique sporangia are placed on an elevated receptacle, which forms a raised point on the surface of the fronds when the sporangia are removed. Of these the Alsophileæ are without true indusia, while the Cyatheæ have a spherical indusium, bursting above or below, and forming a cup round the sorus. The pulpy substance of the stem of Cyathea medullaris was a common article of food with the New Zealanders. The Gleichenineæ have a creeping or climbing rhizome, and globose or trigonal sporangia, few in number, and disposed in a radiating manner, so that the narrow end is internal. They are often seated in a little cavity, and are highly deciduous. The fronds are generally forked or trifid, the middle division being sometimes supplied with a little bulb-like body. They are mostly tropical or subtropical plants, but some species grow in Chili, New Zealand, and Japan. The Trichomanineæ are pretty well distinguished from other ferns by their pellucid membranaceous texture. As regards their technical characters, they have an oblique and complete ring to the sporangia, which are of a lenticular form, and are collected about a more or less elongated receptacle, which is free within either an urn-shaped cup or a two-valved indusium, projecting from the edge of the frond. They are chiefly inhabitants of the moist tropical forests, or extra-tropical regions of damp and mild temperature. Great Britain only owns one species of the genus Trichomanes, and two of the genus Hymenophyllum, while species of these two genera constitute one-fifth of the fern vegetation of our antipode islands of New Zealand. It is more than doubtful even that the Trichomanes radicans, or Bristle fern, is indigenous, as it is found in no other part of Great Britain except the Irish counties of Cork and Kerry, growing on dripping rocks and waterfalls, or depending from the walls and roofs of caverns; and as it is also found in the West Indies and the North Atlantic islands its transit may be accounted for, as in other cases. [Illustration: Fig. 68. Trichomanes radicans.]