Tree fern – Sphaeropteris glauca (Blume) R.M.Tryon of Sarawak/Borneo – around 900m ASL.

Sphaeropteris glauca (Blume) R.M.Tryon (Cyatheaceae, order Cyatheales) is a tree-like fern; the name was published in this combination in 1970. Homotypic synonyms include Chnoophora glauca Blume (1828) and Alsophila glauca (Blume) J.Sm.; in some literature, the species also appears under the heterotypic synonym Cyathea contaminans (Hook.) Copel. The natural distribution area is ‘E. Himalaya to W. & Central Malesia’ and explicitly includes Borneo; the species grows predominantly in the humid tropical biome. For Borneo (under Cyathea contaminans), Holttum describes occurrences ‘in clearings and open areas in the forest, especially near streams’ at altitudes of 300–1500 m; in Mount Kinabalu National Park, it is highlighted as the most conspicuous tree fern in the lower elevations. Among other uses, it is documented that the fibrous trunk is used as a substrate in horticulture/orchid cultivation (e.g. as a base for epiphytic orchids).

Etymologically, the genus name Sphaeropteris (first published in 1801) is derived from sphaera/sphaira (‘sphere’) and pteris (“fern”); in older etymological literature, this is attributed to the ‘spherical’ shape of an indusium that encloses the sori. The species epithet glauca is the feminine form of glaucus/glaucous (‘bluish-grey, frosted’); corresponding ‘glaucous’ characteristics are explicitly mentioned in descriptions of the species (e.g. on stipes and leaf undersides).