Atractocarpus Schltr. & K.Krause

Mouly, Arnaud, 2012, On the distinction of Atractocarpus heterophyllus (Montrouz.) Guillaumin & Beauvis. and A. bracteatus Schltr. & K. Krause (Rubiaceae): in search of the correct name for the type species of Atractocarpus Schltr. & K. Krause, Adansonia (3) 34 (1), pp. 103-114 : 106

Genus Atractocarpus Schltr. & K.Krause

Botanische Jahrbücher für Systematik, Pflanzengeschichte und Plflanzengeographie 40 (92): 43 (1908).

— Type: A. bracteatus Schltr. & K.Krause.

DESCRIPTION

Atractocarpus is currently a genus of c. 40 species that occur in Australia, the Federated States of Micronesia, Fiji, Indonesia, New Caledonia, Papua New Guinea, Philippines, Solomon Islands, Society Islands, Tonga and Vanuatu, with the highest diversity in New Caledonia. The New Caledonian species are mostly riparian, living in mesic to humid forests, or more rarely in bushes. The Australian and other Pacific islands representatives occupy various mesic forests, swamp forests and maritime semi-deciduous thickets.

The diagnostic combination of characters for the genus, sensu Puttock (1999) is: flowers with subsessile anthers; styles completely included in the tube; patent corolla lobes; porate pollen grains in monads; ovary bilocular, placentation axile; berries moderate to large, spherical to fusiform, many-seeded; and seeds large with an extensive peripheral hilum.

An interesting characteristic feature also noted by Puttock (1999) consists of the placental mass degenerating into a watery pulp, enclosing seeds. At the fruit stage, the locule limits and the placentation type become consequently not obvious in fruit-section (see Figs 2 ; 3 ).

Figures

FIG. 2. — Atractocarpus bracteatus Schltr.& K.Krause: A, female flower;B, longitudinal section of a female flower (corolla and stamens detached from hypanthium); C, detail of stipules at branch apex; D, entire fruit and longitudinal section of a fruit; E, transversal section of a fruit; F, entire seed and its longitudinal section; G, embryo. Scale bars: A-C, 1.5 cm; D, 6 cm; E, 1.5 cm; F, 5 mm; G, 2 mm. Based on Mouly 149 (P).

FIG. 3. — Atractocarpus heterophyllus (Montrouz.) Guillaumin & Beauvis.: A, view of the apex of a female individual in fruit; B, detail of stipules at branch apex; C, transversal section of a fruit; D, longitudinal section of a fruit; E, developed placenta at fruit stage, in dorsal and ventral views; F, longitudinal section of a seed; G, embryo. Scale bars: A-E, 3 cm; F, G, 2 mm. Based on MacKee 26464 (P) and unpublished N. Hallé’s drawings of New Caledonian Rubiaceae in sched (P).