Isolona linearis Couvreur, 2006

Couvreur, Thomas L. P., Gereau, Roy E., Wieringa, Jan J. & Richardson, James E., 2006, Description of four new species of Monodora and Isolona (Annonaceae) from Tanzania and an overview of Tanzanian Annonaceae diversity, Adansonia (3) 28 (2), pp. 243-266 : 253-254

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Isolona linearis Couvreur

sp. nov.

Isolona linearis Couvreur , sp. nov.

( Fig. 4 View FIG )

Haec species inter congeneros quoad folia glabra, flores axillares etiam lobulos corollinos horizontaliter patentes ad Isolonam hexalobam (Pierre) Engl. & Diels maxime accedit, sed ab ea sepalis triangularibus 2-3 mm longis atque lobulis corollinis anguste lanceolatis usque linearibus distinguitur.

TYPUS. — Tanzania. Iringa Region, Mufindi Distr., Luhega Forest Reserve , 08°21’S, 35°58’E, 20.I.1997, fl., Frimodt-Møller TZ 59 (holo-, C!; iso-, K!) GoogleMaps .

HABITAT. — Moist montane forest, at 1100-1700 m altitude.

DISTRIBUTION. — Only known from Iringa Region in Tanzania ( Fig. 6).

OTHER MATERIAL EXAMINED. — Tanzania. Iringa Region, Mufindi Distr., Lulanda Forest, 8°30’S, 35°30’E, alt. 1450 m, 6.XII.1987, fl., Congdon s.n. (P!). — Mufindi Distr. , Lulanda Forest Reserve , 8°36’S, 35°37’E, alt. 1650 m, 16.II.1979, fl., Cribb 11470 (K!). — Luhega Forest Reserve , Mufindi Distr. , 8°21’S, 35°58’E, alt. 1650 m, 18.II.1996, fl., Frimodt-Møller 5 (C!, K!). — Idem, 8.II.1996, fl., Frimodt-Møller 12 (C!). — Idem, 21.II.1996, ster., Frimodt-Møller 64 (C!). — Idem, 21.II.1996, ster., Frimodt-Møller 66 (C!). — Udzungwa Scarp Forest Reserve , Mufindi Distr. , 8°23’S, 35°25’E, alt. 1550-1700 m, 18.XII.1997, fr., Frimodt-Møller 679 (C!). — Udzungwa Scarp Forest Reserve , Mufindi Distr. , 8°23’S, 35°25’E, alt. 1550-1700 m, 18.II.1997, fl., Horlyck 325 (C!, K!). — Idem, 20.II.1997, fl., Horlyck 359 (C!). — Kilolo Distr. , Ridge above Sanje Falls , 7°46’S, 36°54’E, alt. 1150 m, 24.VII.1983, fl., Polhill 5143 (EA!, K!, MO!). — Mufindi Distr. , Lulanda, 8°36’S, 35°37’E, alt. 1500 m, 24.XI.1998, fl., Gereau 2552 (MO!, NY!). — Idem, 25.I.1989, ster., Gereau 2882 (MO!, P!). — Mufindi Distr. , Lulanda Forest , isolated patch of closed high forest on Uzungwa escarpment, 8°40’S, 35°35’E, alt. 1430 m, 6.IX.1986, fl., Lovett 592 (MO!). — Kilolo Distr. , Mwanihana F. R. above Sanje Village , moist forest on edge of Gologolo Mountains overlooking the Kilombero flood plain, 7°45’S, 36°55’E, alt. 1250 m, 17.VI.1986, fl., Lovett 861 (MO!). — Kilolo Distr. , Udzungwa Mountains National Park , Mt. Luhomero , 7°47’S, 36°49’E, alt. 1200 m, 23.IX.2001, fl., Luke 7732 (EA!). — Kilolo Distr. , Mwanihana Forest Reserve above Sanje Village , 7°50’S, 36°55’E, alt. 1400-1700 m, 10.X.1984, ster., Thomas 3899 (MO!) GoogleMaps .

No location indicated, alt. 1650 m, 23.II.1996, fl., Mikkelsen 384 (K!).


Tree to 15 m tall; bark dark brown to black, smooth; young branchlets glabrous, smooth. Petiole 4-5 mm long, 1.0- 1.5 mm in diam., glabrous, verrucose; leaf blade obovate to elliptic, 14-18(-25) × 5-7(-9) cm, coriaceous, short- to long-acuminate at apex, round- ed to cuneate at base, glabrous; midrib prominent below; secondary veins 11 to 13 pairs, anastomosing 2-3 mm from margin; tertiary venation intermediate between percurrent and reticulate.

Flowers axillary and pendulous, solitary; pedicel in flower (3-) 5-10 mm long, in fruit 10-15 mm long, glabrous; bracts 3, inserted at base of pedicel, c. 1 mm, the margins ciliate. Sepals triangular, 2-3 × c. 3 mm, acute at apex, usually persistent in fruit, the margins white-ciliate; corolla cupulate, glabrous, pale red, verrucose when dried, with tube 4-5 mm long, the lobes patent, 10-30 × 3-4(-8) mm, lanceolate to linear, sometimes elliptic, rounded at apex, narrowed at base, fleshy, greenish, sparsely ciliate when very young, glabrous and bronzy-red when mature; stamens flat, glabrous, c. 1.1 mm long, the connective appendages c. 0.1 mm long; gynoecium 0.2 mm long topped by glabrous stigma.

Fruit c. 5 cm long, 2-3 cm in diam., irregularly elliptic, with caudate apex c. 1 cm long, furrowed, green tinged with white; seeds 10-15 mm long, smooth, light brown.

Pollen: monad, apolar, globose. Size at longest axis:monad, 35-40 µm.Tectum structure: rugulate, coarse ( Fig. 7G, H View FIG ).


Mulinditi (Kihehe).


Isolona is very variable in floral characters. Flowers seem to continue growth after anthesis and before abscission, resulting in considerable polymorphism. Isolona linearis and I. hexaloba are both very polymorphic. The shape and size of the corolla lobes in I. linearis vary, with the predominant shape being linear. One other striking feature is that some flowers of various specimens of I. linearis have five corolla lobes instead of six, which could indicate a tendency towards pentamery. This tendency is also observed in I. campanulata Engl. & Diels (Adam 1971) .