Homalium pseudoboinense Appleq.

Wendy L. Applequist, 2016, Revision of the Malagasy species of Homalium sect. Eumyriantheia Warb. (Salicaceae), Candollea 71 (1), pp. 33-60 : 50-52

10. Homalium pseudoboinense Appleq. , spec. nova

( Fig. 2 B-C, 3).

Typus: Madagascar. Prov. Toamasina: env. de la Baie d’Antongil , bassin de la Mahalevona , entre Ankovana et Ambatondradama, III.1953, fl., Service Forestier 8866 ( P [ P04734315 ]! ; iso-: P [ P04734251 , P04734314 , P04734316 , P04734317 ]!).

Homalium pseudoboinense Appleq. differs from H. boinense H. Perrier in having larger flowers, stamens in groups of 3, and sepals with densest pubescence near margins.

Tree described as large; large twigs brown; young twigs brown, glabrous; stipules narrowly lanceolate, 1.6-3 mm, glabrous to minutely pubescent, occasionally persistent. Leaves alternate; petiole 6-14 mm, glabrous or glabrate; blade broadly elliptical, 5-10.7 × 3.5-6.2 cm; base convex to rounded (to broadly cuneate, sometimes minutely attenuate at petiole attachment); apex rounded to cuspidate or emarginate; margins subentire, revolute, usually with 1 or more small glands in margins not associated with toothing; abaxial surface glabrous, drying brown; adaxial surface glabrous, drying darker brown. Inflorescences paniculate, with well-separated, few-flowered short side branches, at least the upper portions mostly racemiform, lateral, largely confined to twig apices, 5-15 cm, moderately to densely pubescent with very short appressed hairs; peduncle (0.2-) 1-3.5 cm, thick and somewhat angular; pedicel 3.5-11 mm, short-pubescent; bracts broadly ovate to suborbicular, 1.3-2.3 mm, pubescent; bracteoles lanceolate to ovate, 1.5-2.8 mm, pubescent. Flowers: sepals 5, elliptical with rounded to broadly acute apex, 5.5-6 mm, abaxial surface short appressed-pubescent, the margins usually broad, pale and more densely pubescent than central portions above the base; calyx cup very shortly funnelform to cup-shaped, short appressedpubescent; sepal glands irregularly trapezoid, sometimes elevated, possibly 2-lobed, 1.3-1.4 × 0.7-0.8 mm, upper surface densely pubescent; petals obovate with rounded apex, mostly ascending, 9-10.5 × 4.2-5.4 mm, much longer than sepals, abaxial surface appressed-pubescent, densely so at base and in center, adaxial surface glabrous; stamens in groups of 3 or 4; filaments 3-3.6 mm, glabrous; anthers 0.4 mm; ovary conic, densely villous; styles (4-)5, 1.5-2 mm, pubescent at base. Seeds not seen.

Homalium pseudoboinense is known from only a single collection, which is over 60 years old. The locality is inland humid forest, close to the boundary between Toamasina and Antsiranana provinces, at around 500 meters in elevation. The lack of collections from a well-botanized region of Madagascar suggests that the species is likely to be very rare or a highly localized endemic. However, the type locality may be within the boundaries of the protected area of the Masoala National Park, reducing the threat of imminent extinction. In view of the lack of information available for this species, a preliminary conservation status assessment of “Data Deficient” [DD] seems most appropriate.

Notes. – Homalium pseudoboinense most closely resembles the sole western species of the section, H. boinense , but has much larger flowers with only 3 stamens per bundle and sepals more densely pubescent towards the margins; the latter character is quite unusual. Of the other species around the Baie d’Antongil, it most closely resembles the large-leaved, sometimes large-flowered littoral species H. nobile , which has a racemose inflorescence and sepals most densely sericeous in the central portions, sometimes appearing keeled, and only slightly shorter than the petals.

Figures

Fig. 2. – Flowers of newly described species of Homalium sect. Eumyriantheia Warb. A. Homalium dorrii Appleq.: flowers and nearly mature fruit with single seed; B. Homalium pseudoboinense Appleq.: abaxial surface of perianth; C. Homalium pseudoboinense: open flower; D. Homalium randrianasoloi Appleq.; E. Homalium ranomafanicum Appleq.; F. Homalium schatzii Appleq.: open flower; G. Homalium schatzii: abaxial surface of perianth.