Homalium schatzii Appleq.

Wendy L. Applequist, 2016, Revision of the Malagasy species of Homalium sect. Eumyriantheia Warb. (Salicaceae), Candollea 71 (1), pp. 33-60 : 55-58

14. Homalium schatzii Appleq. , spec. nova

( Fig. 2 F-G, 6).

Typus: Madagascar. Prov. Toamasina: 1-2 km E of Fampanambo, 15°22’35’’S 49°37’46’’E, 20 m, 28.I.1999, fl., Schatz et al. 3850 (holo-: P [ P04705556 ]! ; iso-: G!, K!, MO!, TEF).

Homalium schatzii Appleq. differs from H. randrianasoloi Appleq. in its racemose inflorescence, larger sepal glands, and abaxial surface of petals densely appressed-pubescent with a pronounced narrow glabrate stripe.

Tree to 16 m tall; large twigs pale brown; young twigs pale brown, glabrous; stipules deltoid, 0.5 mm, glabrous. Leaves alternate; petiole 5-8 mm, glabrous; blade elliptical to obovate, 6-11.5 × 2.8-6.2 cm; base convex; apex rounded to roundedcuspidate, rounded-obtuse or emarginate; margins subentire with 1-2 small basal glands per side; abaxial surface glabrous, drying brown; adaxial surface glabrous, drying dark brown. Inflorescences racemose with flowers borne in groups of 1 to 3 at the termination of a prominent ridge, lateral, 5-8.3 cm, glabrous proximally to minutely pubescent distally; peduncle 3.5- 4.3 cm, noticeably flattened; pedicel 3-5 mm, minutely pubescent; bracts deltoid, 0.3-1.5 mm, glabrous; bracteoles usually absent. Flowers: sepals 4, narrowly oblong to oblong-ovate with rounded (to rounded-acute) apex, 3.4-4.6 mm, abaxial surface glabrate to sparsely and minutely pubescent; calyx cup funnelform, glabrate to sparsely and minutely pubescent; sepal glands roughly trapezoid to elliptical or nearly square, 0.9-1.6 × 0.7-1 mm, upper surface glabrous; petals obovate with rounded apex, 4.7-6.5 × 2.4- 2.8 mm, much longer than sepals, abaxial surface moderately to densely short appressed-pubescent with a conspicuous glabrate stripe down center, adaxial surface glabrous; filaments 2.4-3.2 mm, glabrous; anthers 0.4 mm; ovary conic, short-pubescent; styles 4-5, 2- 2.5 mm, short appressed-pubescent especially at base. Seeds not seen.

Distribution, ecology and conservation status. – Homalium schatzii is native to low-elevation humid forest on laterite in northeastern Madagascar; it is known from only the type collection, from a locality that is subject to ongoing degradation. As for H. pseudoboinense , from a quite different habitat but also near the Baie d’Antongil, the dearth of specimens despite a relatively large number of collections made in that region of Madagascar allows the presumption that the species is very rare or a highly localized endemic. Thus a preliminary conservation status assessment of “Critically Endangered” [CR B2ab(iii)] seems appropriate.

Notes. – Homalium schatzii is part of the H. capuronii group (see Table 1 ), and is the only species of that group that occurs near Masoala in the northeast. It is distinguished within that group of species by the combination of racemose inflorescences, very large sepal glands, and an unusual pattern of corolla indument, glabrate in a stripe down the center but often relatively dense to near the apical margins, where most species have sparser indument. Two other large-leaved species, H. nobile and H. pseudoboinense , occur in the same region. Both have larger, 5-merous flowers that have dense sepal indument and lack the unusual corolla indument seen in H. schatzii .

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.