Alsophila exilis

Cyatheaceae

 Alsophila exilis (Holttum) Lehnert

Link to Australian Plant Name Index for publication details and synonyms: https://id.biodiversity.org.au/name/apni/51350865

Rhizome erect to 4 m tall, 4–8 cm diam., suckering from rhizome buds, with 1 bud near each stipe base. Stipe c. 20 cm long; stipe towards base with 0.5–1.5 mm long blunt spines, each spine bearing a caducous dull brown scale; scales c. 10 mm long and 1 mm wide; base thickened; margins fragile, sometimes setiferous; apex setose. Lamina to 100 cm long, thin; longest pinnae to 30 cm long; basal pinnae to 18 cm long; pinna rachis smooth, a few very narrow scales basally; pinnules to 5.2 cm long, 1.5 cm wide, deeply lobed; lobes at an angle of c. 60°, crenate, acute; veins to 7 pairs, those on fertile pinnules mostly forked; scales near bases of pinnule costae ovate; larger scales brownish, apically setiferous; smaller scales pallid, not setiferous; distal scales and those on costules small, bullate, sometimes with filiform apices; upper surface of costae bearing rather sparse antrorsely curved slender brown hairs. Sori medial, near the forks of veins; exindusiate, with few very small scales around receptacle; paraphyses longer than sporangia, distally flexuous, thickened at their bases. 

Endemic to Australia and known from only one locality on CYP.

Terrestrial in spring-fed creeks in rainforest.

This is a rare and localised endemic tree-fern.

Similar to Sphaeropteris felina. It is also very similar to Alsophila macgillivrayi from Papua New Guinea and the Louisiade Archipelago. Alsophila exilis is distinguished by its shorter stipe (c. 20 cm long cf. to 1 m in Sphaeropteris felina) and distinctly reduced basal pinnae ( cf. only slightly reduced in Sphaeropteris felina).