Cyathea affinis is a variable species of tree fern native to Fiji, Samoa, the Cook Islands, Austral Islands, Tahiti, and the Marquesas Islands. The trunk of this plant is erect and 2–6 m tall. Fronds are bipinnate and 2–3 m in length. The rachis and stipe are pale to brown in colour, or flushed with red towards the pinnule rachis. The stipe is sparsely covered in narrow basal scales, which are pale to dark and have broad fragile edges. Characteristically of this species, the lowest one or two pairs of pinnae may be slightly reduced and occur towards the base of the stipe. Sori are located near the pinnule midvein and are partially or fully covered by indusia, which open towards the pinnule margin.
Cyathea acrostichoides is a species of tree fern native to the Maluku Islands and Western New Guinea, where it grows in forest and disturbed sites at an altitude of 650–1100 m. The trunk is erect and usually 1–3 m tall. Fronds are bipinnate and 1–2 m long. The stipe is slender and covered with spines. It is sparsely covered with medium brown scales. Sori cover most of the underside of fertile pinnules. C. acrostichoides lacks indusia.
Cyathea aneitensis is a species of tree fern native to Vanuatu and possibly New Caledonia. This species has an erect trunk up to 3 m tall. Fronds are bipinnate and may reach 2 m in length. The rachis and stipe are either very dark and smooth or have a few scales towards the base of the stipe. The scales are dark and narrow. Sori occur near the pinnule midvein and are covered by large, thin, fragile indusia. The closest relative of C. aneitensis appears to be Cyathea vieillardii. It can be distinguished from that species by its very dark stipes and frond bases.
Cyathea batjanensis is a species of tree fern native to the Maluku Islands and western New Guinea, where it grows in rain forest at an altitude of approximately 600 m. The trunk is erect and 2–3 m tall. Fronds are bi- or tripinnate and 1–2 m long. The stipe is spiny, warty and covered with scattered scales that are dark brown and have fragile edges. Sori are round and occur near the fertile pinnule midvein. They are covered by small, narrow indusia that resemble small saucers in appearance.
Cyathea brooksii is a species of tree fern native to Cuba, Hispaniola and Puerto Rico, where it grows on serpentine soils in shaded ravines, along streams, and on forested slopese at an altitude of 250–950 m. The trunk is prostrate and only about 6 cm in diameter. Fronds are pinnate or bipinnate and up to 2 m long. The base of the rachis is covered with blackish scales that have a paler margin. Sori occur in two rows, one along each side of the pinnule midvein.
Cyathea cincinnata is a species of tree fern native to eastern New Guinea, where it grows at an altitude of 1300 m or higher. It is known only from a few collections in the Sepik region. The trunk is erect and short. Fronds are bi- or tripinnate and 1-1.5 m long. The stipe bears many glossy brown scales that have a distinctive black central band and dull edges. Sori are round, occur near the fertile pinnule midvein. They are covered by firm, brown indusia that are cup-like in appearance.
Cyathea coactilis is a rare species of tree fern known only from the southern highlands of Papua New Guinea, where it grows in alpine shrubland at an altitude of about 3000 m. The trunk is erect and 2–3 m tall. Fronds are bi- or tripinnate and usually 1–2 m long. Characteristically of this species, they occur in two whorls of about ten fronds each. The underside of the rachis is covered with small, pale scales. The stipe is covered with pale scales that have dark, narrow and fragile edges. Sori are round and are covered by thin indusia that are cup-like in appearance. They occur near the fertile pinnule midvein.
Cyathea costalisora is a species of tree fern native to western New Guinea, where it grows on the edges of forest and in moist hollows at an altitude of 1900–3225 m. The trunk is erect, up to 4 m tall and may branch near the base. Fronds are bi- or tripinnate and 1-1.5 m long. The stipe is warty, especially where scales have fallen. The scales are pale and have a distinctive dark glossy central region, with a paler dull margin. Sori are round and occur near the fertile pinnule midvein. They are covered by firm, dark indusia that are cup-like in appearance.
Cyathea cucullifera is a species of tree fern native to eastern New Guinea, where it grows in montane forest at an altitude of about 2400 m. The trunk is erect and 2–3 m tall. Fronds are bi- or tripinnate and 2–3 m long. Characteristically of this species, they occur in two whorls of four to six fronds each. The stipe is warty and covered with scales. The scales are dark, glossy, have a narrow paler margin and are large towards the base. Sori occur near the fertile pinnule midvein and are covered by thin, pale brown indusia that are scale-like in appearance.
Cyathea dicksonioides is a species of tree fern native to northeastern New Guinea, where it grows in grassland at an altitude of 2600–2900 m. It is a relatively uncommon species. The erect trunk may be 3 m tall or more and about 20 cm in diameter. Fronds are bi- or tripinnate and approximately 1 m long. They are erect and bristly, forming an irregular crown. The fronds occur in two whorls of 10-12 fronds each, with the inner of the two whorls bending downward towards the trunk. The stipe is covered with glossy scales that have narrow, pale and fragile edges. Two to four sori occur per fertile pinnule. They are covered by firm, pale indusia that are hood-like in appearance.
Cyathea eriophora is a species of tree fern native to eastern New Guinea, where it grows in wet ravine forest at an altitude of 1400–2000 m. The trunk is erect and 2–3 m tall. Fronds are bi- or tripinnate and 2–3 m long. The stipe is dark and covered with spines and scales. The scales are variable, being either small and pale or large with a dark apex. Sori occur near the fertile pinnule midvein and lack indusia.
Cyathea geluensis is a species of tree fern native to central and eastern New Guinea as well as the Louisiade Archipelago, where it grows in mossy forest. In New Guinea itself, plants grow at an altitude of 1000–2000 m, however they are present at lower elevations of 700–900 m on associated islands. The trunk of this tree fern is erect and may be 5 m tall or more. Fronds are bi- or tripinnate and 1-2.5 m long. They are usually about ten live fronds present in the crown at once. The stipe may be warty and/or have short spines as well as many scattered scales towards the base. These scales are pale to dark and have dull, fragile edges. Sori occur near the fertile pinnule midvein and are protected by pale, thin indusia. C. geluensis is a variable taxon and further study is needed to determine whether it does not in fact represent a species complex.
Cyathea gleichenioides is a species of tree fern endemic to New Guinea, where it grows in open peaty grassland and on forest margins, often in groups, at an altitude of 2800–3700 m. The trunk of this plant is erect, up to 3 m tall and about 24 cm in diameter. The narrow fronds are tripinnate and about 1 m in length. Around 60 fronds form a rounded crown.The stipe is warty and bears scattered scales towards the base. These scales may be either glossy brown with a paler dull margin, or small, pale and fringed. Sori occur one or two per fertile pinnule and are protected by firm, brown indusia.
Cyathea gregaria is a species of tree fern endemic to eastern New Guinea, where it grows in lowland forest and coastal rain forest, often forming clumps, at an elevation of up to 100 m. The trunk of this plant is erect and usually 4–5 m tall and about 10 cm in diameter. Fronds may be bi- or tripinnate and 2–3 m in length. The stipe bears spines, but has few scales. These scales are medium brown in colouration and have a paler margin. Sori occur near the fertile pinnule midvein and lack indusia.
Cyathea horridula is a species of tree fern native to western New Guinea, where it grows in montane forest at an altitude of approximately 1700 m. It is a rare plant known only from the type locality. This plant has an erect trunk up to 3 m tall or more. Fronds may be bi- or tripinnate and 1–2 m in length. The stipe is covered with spines and bears scattered scales towards the base. These scales are pale and have fragile edges. Sori are borne near the fertile pinnule midvein. They are protected by small, dark brown indusia that are saucer-like in appearance.
Cyathea imbricata is a species of tree fern endemic to Western New Guinea, where it grows in open forest at an altitude of 3240 m. The trunk of this plant is erect and approximately 2 m tall. Fronds may be bi- or tripinnate and are usually less than 1 m in length. The stipe is dark, spiny, and covered with caducous scales. These scales are glossy brown in colouration and have a paler margin and fragile edges. Sori are borne in groups of one to four per pinnule lobe. They are protected by firm indusia.
Cyathea insulana is a species of tree fern native to New Guinea, where it grows in mossy forest and ravines at an altitude of 750–1600 m. The trunk of this species is erect, 8–10 m tall, and 14 cm in diameter. Fronds may be bi- or tripinnate and approximately 3 m in length. They form a spreading crown. The stipe bears thick spines as well as scales. These scales are either small, pale brown, with a short fringe, or large and glossy brown, with fragile edges. Sori are borne near the fertile pinnule midvein. They are protected by thin, pale indusia.
Cyathea kanehirae is a species of tree fern native to western New Guinea, where it grows in montane forest at an altitude of 1600–2700 m. The trunk of this plant is erect and 1–4 m tall. Fronds may be bi- or tripinnate and 1–2 m in length. The rachis is smooth, while the stipe is dark and warty. The stipe is covered with flat, brown, scattered scales. Sori are borne near the fertile pinnule midvein. They are protected by small indusia that are cup-like in appearance.
Cyathea klossii is a species of tree fern native to western New Guinea, where it grows in rain forest from the lowlands up to an elevation of about 750 m. The trunk of this plant is erect, 1–2 m tall, and only 1–2 cm in diameter. Fronds are pinnate and usually 0.5–1 m in length. The stipe bears thick, dark scales that are dull in appearance. Sori occur near the fertile pinnule midvein. They are protected by thin, pale, fragile indusia.
Cyathea ledermannii is a species of tree fern native to Papua New Guinea and Bougainville Province in the Solomon Islands, where it is common in submontane rain forest at an altitude of 1000–3000 m. The trunk of this plant is erect and grows to about 3 m in height. Fronds may be bi- or tripinnate and up to 2 m in length. The rachis is purplish brown in colouration and usually bears basal scales. These scales range from pale, to brown, to bicoloured. Sori are borne on each side of the pinnule midvein. They are protected by firm indusia.
