Cyathea boivinii 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 : 318-319

33. Cyathea boivinii Mett. ex Kuhn

REMARKS

Cyathea boivinii is a diffi cult species widespread in Madagascar and on the Comoros and exhibits a high intraspecific variability of indusium and indument characters as well as of the degree of lamina dimorphism and pinnule dissection.Several formerly described species and varieties have been reduced to synonyms because of continuous character variation. Th e varietal key provided below is an attempt to formally recognize discrete character variation within this taxon, although the determinations of a minority of specimens may remain ambiguous. All varieties of C. boivinii have cup-shaped, never globular, indusia and large pinnae with a usually sparse to absent abaxial lamina indument.

KEY TO THE VARIETIES OF CYATHEA BOIVINII

1. Petiole in most specimens without scales (i.e. the scales are rapidly caducous); petiole and rachis covered with an abundant and persistent tomentum of intricate hairs and squamules; all leaves are apparently periodically and simultaneously shed; Andringitra massif ................................................................................................ 33b. var. andringitrensis

— Petiole in most specimens with scales (i.e the scales are persistent); petiole and rachis glabrous or with a conspicuous and caducous squamulate tomentum; leaves not simultaneously shed; not restricted to the Andringitra massif .................................................... 2

2. Petiole scales reaching the first pinna pair, a noticeable sparse tomentum of crispate hairs on the abaxial face of the costulae is always present .............................. 33c. var. bevolo

— Petiole scales restricted to the lower half of the petiole, abaxial face of the costulae glabrous or with a caducous tomentum of crispate hairs ........................................................... 3

3. Fertile and sterile pinnules slightly to strongly dimorphic, surface of the petiole base usually finely muricate ( Fig. 32N) ........................................................... 33a. var. boivinii

— Fertile and sterile pinnules monomorphic, surface of the petiole base coarsely muricate ( Fig. 34K ) .................................................................................................................. 4

4. Mature indusia shallowly cup-shaped, at most hemispherical, with an entire rim .......... ................................................................................................... 33d. var. hildebrandtii

— Mature indusia hemispherical to profoundly cup-shaped, dehiscing in lobes or with ir- regular slits, their rim not entire ........................................... 33e. var. parahildebrandtii

Figures

FIG. 34. — A-F, H-L, Cyathea boivinii Mett. ex Kuhn var. hildebrandtii; A, pinnules abaxially with a fragment of the costa, common form,sori only partly indicated; B, pinnules abaxially with a fragment of the costa,form with broader pinnule segments,sori only partly indicated; C, pinnule segments abaxially with a fragment of the costula, form with broader pinnule segments; D, E, pinnule segments abaxially with a fragment of the costula,common forms; F, habit; H, sori,common form with long receptacles and cup-shaped indusia with entire rims; I, scales from the base of the petiole, form with narrow, blackish scales; J, scales from the base of the petiole, common form; K, basal part of the leaf (from the petiole base up to the first pinna pair), lateral view, one half of the petiole pruned away by longitudinal section, note the presence of a pair of reduced pinnae at about 20 cm above the base of the petiole; L, leaf scars and trunk surface; G, C. boivinii var. parahildebrandtii Janssen & Rakotondr., mature sori with dehiscing indusia. A, D, H, J, K, Rakotondrainibe 1666 (P); B, C, Rakotondrainibe 4709 (P); E, I, Janssen et al. 2956 (P); F,Janssen et al. 2442 (P); G,Rakotondrainibe et al. 6730 (P); L, Janssen et al. 2464 (P). Scale bars: A, B, L, 1 cm; C-E, G, H, 0.1 cm; F, 1 m; I, J, 0.5 cm; K, 5 cm.