Cyatheaceae

Caudex massive, usually erect and unbranched, where prostrate not dorsiventral in structure; fronds arranged on caudex in spiral series; vascular system of caudex a hollow cylinder with gaps corresponding with leaf-bases, in some cases small medullary bundles also present; a cylinder of very hard sclerenchyma, with gaps at leaf-bases, present both inside and outside the vascular cylinder (but absent in Cibotium), the surfaces of the sclerenchyma covered with cubical cells containing silica; tangentially arranged sieve-tubes present in the phloem as well as longitudinal ones. Stipes of Cyathea containing numerous small vascular strands arranged in 3 series (fig. 6), these strands more or less united in smaller axes of Cyatheafronds and also in larger axes of other genera (fig. 31f, 33d); stipe-bases persistent, or sooner or later caducous leaving a pattern of scars on the caudex; pneumathodes present along each side of stipe, in a single discontinuous or almost continuous row, or in 2—3 rows close together, the row joining upwards to a similar row on the basiscopic side of the first pinna, a ± circular pneumathode at the base of the pinna beginning the row on the main rachis to the next pinna. Dermal appendages on fronds: multiseptate hairs only, or both hairs and scales (Cyathea); if both, the hairs often confined to the adaxial surface of the fronds. Fronds in most cases bipinnate-tripinnatifid, with varying gradations to tripinnate, in a few cases simply pinnate, in Culcita 3—4-pinnate; pinnules almost symmetrical at the base except in Culcita; veins normally free except in Cyathea capitata and in the genus Cnemidaria (trop. America). Sori either terminal on veins and protected by an inner indusium as well as by the more or less reflexed edges of a small lobe of the lamina (outer indusium), or apparently not terminal on veins and not near the edge of the lamina, with indusia of various form or without indusia; receptacle of various shape, in all cases containing vascular tissue which in the case of Cyathea represents the termination of a short vein; stalks of sporangia short or long, 4 or more cells in transverse section, annulus more or less oblique, with a more or less clearly defined lateral stomium; spores trilete, surfaces smooth or variously sculptured; multiseptate paraphyses, of a single row of cells (terminal cell glandular or not) or scale-like at the base, present with sporangia. Distribution. Throughout the wetter parts of the tropics, especially on mountains; a few species just north of the tropics, more south of the tropics especially in Australasia. As here construed, 9 genera, of which 5 are Malaysian: Cyathea (pantropic, at least 600 spp.); Cnemidaria (limited to species with pinnate fronds, anastomosing veins and distinctive spores, tropical America, 10 spp.); Lophosoria (tropical America, monotypic); Dicksonia (tropics and southern subtropics in Malaysia, Australasia, America, St Helena, c. 25 spp.); Cystodium (Malaysia, monotypic); Thyrsopteris (Juan Fernandez, monotypic); Culcita (subg. Culcita in Azores and tropical America; subg. Calochlaena in Malaysia and Australasia; in all c. 7 spp.); Cibotium (SE. Asia, Malaysia, Hawaii, Central America, c. 12 spp.); Metaxya (tropical S. America, monotypic).