Cyathea decrescens Mett. ex Kuhn

Janssen, Thomas & Rakotondrainibe, France, 2008, A revision of the indusiate scaly tree ferns (Cyatheaceae, Cyathea subgen. Alsophila sect. Alsophila) in Madagascar, the Comoros and the Seychelles, Adansonia (3) 30 (2), pp. 221-376 : 244-245

5. Cyathea decrescens Mett. ex Kuhn

REMARKS

Varieties of this taxonomically difficult species are defined here primarily based on the degree of lamina dissection. Characters proposed in previous treatments (Tardieu-Blot 1951), such as pinnule shape and axial indument, are not sufficiently discriminative within this taxonomic complex. Indurated, shiny black and arched petiole scales are common to all varieties of this species.

KEY TO THE VARIETIES OF CYATHEA DECRESCENS

1. At least the first five proximal pinnule pairs free, sessile to petiolulate, the following pinnules progressively adnate to the costa, adnate for their entire width only from above the middle of the pinna ............................................................................ 5d. var. quadrata

— At most the first two proximal pinnule pairs free, sessile, all other pinnules broadly adnate to the costa for their entire width ............................................................................... 2

2. Pinnules 2.5-3.5 × 0.3-0.4 cm, spaced by at least their width; trunk 8-10 cm in diameter ............................................................................................................. 5a. var. cristata

— Pinnules (1-)1.5-2 × 0.4-0.6(-0.8) cm, spaced by less than their width; trunk up to 6 cm in diameter ................................................................................................................. 3

3. Aphlebia present; petiole scales strongly indurated and arched, not bullate .................... .......................................................................................................... 5b. var. decrescens

— Aphlebia absent; petiole scales less strongly indurated and only slightly arched, with a slightly bullate base ................................................................. 5c. var. manongarivensis