Homalium sect. Blackwellia Benth.

Applequist, Wendy L., 2016, A reconsideration of the infrageneric classification of Homalium Jacq. (Salicaceae), Candollea 71 (2), pp. 231-256 : 251-252

3. Homalium sect. Blackwellia Benth.

in J. Proc. Linn. Soc., Bot. 4: 33. 1859.

÷ Homalium subg. Blackwellia (Benth.) Warb. in Engler & Prantl, Nat. Pflanzenfam. III(6a): 35. 1893. ÷ Blakwellia Comm. ex Lam., Encycl. 1: 428. 1785 [nom. illeg.] [non Blakwellia Scop. ].

Typus: Homalium paniculatum (Lam.) Benth. (÷ Blakwellia paniculata Lam. ) (designated by Sleumer, 1954: 52).

= Astranthus Lour., Fl. Cochinch. 1: 221. 1790. Typus: Homalium cochinchinensis (Lour.) Druce. (÷ Astranthus cochinchinensis Lour. ).

= Pythagorea Lour., Fl. Cochinch. 1: 243. 1790. ÷ Homalium sect. Pythagorea (Lour.) Kuntze in Post & Kuntze, Lex. Gen. Phan., Prop.: 285. 1903. ÷ Homalium subg. Pythagorea (Lour.) Sleumer, Fl. Males., ser. 1, 5: 52. 1954. Typus: Pythagorea cochinchinensis Lour.

= Homalium sect. Eublackwellia Warb. in Engler & Prantl, Nat. Pflanzenfam. III(6a): 35, 36. 1893. Lectotypus (designated here): Homalium paniculatum (Lam.) Benth. (÷ Blakwellia paniculata Lam. ).

= Homalium sect. Paniculata S.S. Lai [as Paniculatae], Bull. Bot. Res., Harbin 14: 222. 1994 [nom. illeg.] [non Homalium [unranked] Paniculata Benth.]. Typus: Homalium phanerophlebium F.C. How & W.C. Ko.

= Homalium sect. Racemosa S.S. Lai [as Racemosae], Bull. Bot. Res., Harbin 14: 223. 1994 [nom. illeg.] [non Homalium [unranked] Racemosa Benth.]. Typus: Homalium ceylanicum (Gardner) Benth. (÷ Blackwellia ceylanica Gardner ).

Stipules axillary, free. Inflorescences racemose (to spicate) or paniculate; bracts usually small or narrow, caducous, bracteoles absent (sometimes possibly very small and rapidly caducous). Flowers pedicellate to subsessile (sessile) with pedicels usually short, articulated (at least post-anthesis); perianth 5-12(-15)- merous. Sepals ligulate to narrowly elliptical (linear, oblong; seldom much reduced), usually modestly accrescent; calyx tube turbinate to narrowly funnelform or tubular, at least in fruit (seldom short, funnelform), usually prominently ridged; sepal glands usually small and rounded, rarely elliptical. Petals similar in shape and size to sepals or narrowly elliptical to spatulate or oblanceolate (narrowly obovate, oblong-ovate, narrowly deltoid) and markedly longer than sepals, ascending to spreading (usually only in a few flowers at one time), usually modestly accrescent; sepals and petals usually ciliate, usually with long and/or stiff trichomes. Stamens 1 per petal, inserted between glands; anthers dorsifixed, broadly oblong-elliptical with oblong-elliptical locules and a large connective, the slits of dehiscence nearly parallel, or broader than long, usually small, with subglobose locules diverging at a broad angle, slits of dehiscence often toward the apex; Upper surface of ovary conical, usually narrowly, in flower, more prominently so in fruit; styles (2-)3-5(-6, or reportedly 7 in H. barandae ), free to near base. Locule of fruit usually elongated (rarely to subglobose in very short-flowered species), conical above, pubescent (to glabrate) at least on lower portion; seeds usually several per fruit, small, confined to apical portion of ovary.

Distribution. – Asia, Malesia, Pacific to Australia, Madagascar, Mascarenes, South Africa.

Species included. – Homalium acutissimum Gilg , H. axillare (Lam.) Benth. , H. barandae S. Vidal ex Fern. -Vill., H. bismarckense Craven , H. brachybotrys (F. Muell.) F. Muell. , H. brachyrhachis Sleumer , H. brevidens Gagnep. , H. breviracemosum F.C. How & W.C. Ko , H. caput-avis Craven , H. cauliflorum H. Perrier , H. ceylanicum , H. chasei Wild , H. cochinchinense , H. decaryanum H. Perrier , H. dentatum , H. erianthum (Tul.) Baill. , H. glandulosum Tagana & V.H. Nguyen , H. integrifolium (Lam.) Baill. , H. kainantense Masam. , H. kwangsiense F.C. How & W.C. Ko , H. loheri Merr. , H. longifolium Benth. , H. micranthum (Boivin ex Tul.) O. Hoffm. , H. microphyllum O. Hoffm. , H. mollissimum Merr. , H. multiflorum Merr. , H. myrtifolium Sleumer , H. napaulense (DC.) Benth. , H. panayanum , H. paniculatum , H. paniculiflorum F.C. How & W.C. Ko , H. peninsulare Sleumer , H. perrieri Sleumer , H. petelotii Merr. , H. phanerophlebium , H. reductum Craven , H. retivenium Sleumer , H. rufescens , H. sabiifolium F.C. How & W.C. Ko , H. serratum Guillaumin , H. sleumerianum Lescot , H. stenophyllum Merr. & Chun , H. thuarsianum (Tul.) Baill. , H. tomentosum (Vent.) Benth. , H. viguieri H. Perrier

Notes. – Homalium sect. Blackwellia was intended to be based upon Lamarck’s (1785: 428) genus Blackwellia , but as the generic name is an illegitimate later homonym, Bentham (1859) alone is credited with the name. The later-published sect. Eublackwellia is not a nomenclatural synonym of sect. Blackwellia , but because the name has not been used, it has never been typified. The type designated for sect. Eublackwellia above is chosen to ensure that it will be a synonym of sect. Blackwellia , as it has always been considered to be.

At least two of three African species are distinctly unusual. The petals of Homalium chasei from Zimbabwe can be as few in number as 5, at most short-ciliolate, and unusually different in shape from the sepals. Specimens were not seen, but online images make it appear that the calyx tube is funnelform to relatively short turbinate, and the perianth parts are strongly reflexed after anthesis, which is quite unusual. Homalium dentatum has a very short calyx cup and short-ciliolate petals, appears likely to have rapidly caducous bracteoles or unusually plentiful bracts, and sometimes is reported to have a single large seed ( Sleumer, 1973). The latter species is observed to have Homalium -like anthers, whereas the southern African H. rufescens and all Malagasy species of sect. Blackwellia have small anthers with subglobose locules. These species occur in the region overlapping the strictly southern distribution of H. rufescens and the usually more northerly distribution of species of sect. Symphyostylium, and seem in some ways morphologically intermediate.