Humbertacalia C. Jeffrey

Rabarimanarivo, Marina N., Callmander, Martin W. & Calvo, Joel, 2023, Synopsis of Humbertacalia (Compositae), a genus endemic to Madagascar and Réunion, Adansonia (3) 45 (7), pp. 93-113 : 94-95

Genus Humbertacalia C. Jeffrey

Kew Bulletin 47 (1): 82 ( Jeffrey 1992).

TYPE SPECIES. — Humbertacalia tomentosa (Lam.) C. Jeffrey

(basionym: Eupatorium tomentosum Lam. ).

ETYMOLOGY. — The name Humbertacalia honors the French botanist Henri Humbert (1887-1967), who was devoted to the study of the flora of Madagascar and became the foremost specialist in Malagasy Compositae . The epithet is derived in the same way as some of the other genera of the “ Cacalia ” group (e.g. Monticalia C. Jeffrey , Paracalia Cuatrec. , Pentacalia Cass. ).

DESCRIPTION

Plants scandent, woody, with long stems that usually climb or lean over other plants, generally (1)2-4(10) m long, glabrescent or covered with different types of indumentum composed of multicellular trichomes. Stems cylindrical, usually striate, lenticellate or not. Leaves simple, alternate, petiolate (rarely sessile); leaf laminas 3.5-12 × 2-8 cm, oblong, lanceolate, or broadly ovate, base attenuate to cordate (sometimes somewhat truncate), apex rounded to acuminate, margins entire to dentate (usually remotely mucronate-denticulate), plane, glabrous to slightly arachnoid on the adaxial surface, glabrescent to densely lanate on the abaxial surface, venation pinnate or palmate, conspicuous or not, chartaceous to coriaceous, sometimes slightly fleshy; petioles up to 4 cm long. Synflorescences axillary or terminal, thyrsoid-paniculiform or corymbiform. Capitula homogamous, discoid, sessile to pedunculate (peduncles up to 8 mm); involucres cylindrical, cupuliform, or campanulate, glabrous or covered by indumentum; receptacles flat, usually fimbrillate; involucral bracts (3-)5-10(-13), 1.8-5.3 × 0.6-2.4 mm long; supplementary bracts (calycle) (1-)4-8, 0.3-2.4 mm long. Florets (3-)5-20, hermaphrodite; corollas tubular, 5-lobed, mostly whitish; filament collars barely swollen at base; anther bases sagittate to caudate, anther appendages 2-3-times longer than wide; style branches truncate to obtuse with a crown of sweeping trichomes or penicillate, stigmatic areas usually in two bands. Achenes 1.3-3 × 0.4-0.8 mm, rather cylindrical, 5-10-ribbed, glabrous or pubescent, brownish; pappus usually 1-seriate, of capillary bristles, barbellate, whitish.

NOTES

Pelser et al. (2007) presumed the affiliation of Humbertacalia to subtribe Senecioninae on the basis of its morphology, distribution, and karyology. Although some exceptions exist, the subtribe Senecioninae includes genera characterized by having a balustriform filament collar and stigmatic areas in two bands ( Nordenstam et al. 2009). The Humbertacalia species has usually stigmatic areas in two bands but the filament collars are barely swollen at the base, indeed, they are rather cylindrical in some species.

There are species of Humbertacalia that are extremely variable in leaf shape and indumentum, which makes that these characters become barely useful for distinguishing certain species. On the other side, the character sessile/pedunculate capitula appears to be useful for species separation, however, few specimens remain unidentified because they show a combination of characters that do not match the accepted species as currently circumscribed. Phylogenetic information of this group may contribute to elucidate the species relationships and it could also involve some adjustments in the present taxonomic treatment.

KEY TO THE SPECIES OF HUMBERTACALIA C. JEFFREY

1. Leaves palmately 3(-5)-veined; style branches penicillate; achenes pubescent ............................................. ................................................................................................................ 10. H. tomentosa (Lam.) C. Jeffrey

— Leaves pinnately veined; style branches with a crown of sweeping trichomes; achenes mostly glabrous ........ 2

2. Leaves subsessile, base amplexicaul to semi-amplexicaul .................... 2. H. amplexifolia (Humbert) C. Jeffrey

— Leaves petiolate, base attenuate to subcordate .............................................................................................. 3

3. Involucral bracts 5; leaves glabrous, coriaceous ............................................................................................ 4

— Involucral bracts 8-13; leaves glabrous or with indumentum, coriaceous or chartaceous .............................. 5

4. Capitula pedunculate, not clustered; peduncles 2-4 mm long ........... 7. H. neoalleizettei (Humbert) C. Jeffrey

— Capitula sessile or subsessile, usually arranged in glomerules ............. 8. H. pyrifolia (Bojer ex DC.) C. Jeffrey

5. Capitula mostly pedunculated, not arranged in glomerules ......................................................................... 6

— Capitula sessile or subsessile, usually arranged in glomerules ....................................................................... 8

6. Involucral bracts 12-13, arachnoid-floccose (at least at base); leaves initially arachnoid; peduncles 6-15 mm long ............................................................ 5. H. diffusa J. Calvo, Rabarim. & Callm. , comb. nov., stat. nov.

— Involucral bracts 8(-9), glabrous; leaves glabrous; peduncles 1-5 mm long ................................................... 7

7. Involucral bracts 1.8-2 mm long; florets c. 10 ................................................................................................. ............................................ 1. H. abbreviata (Humbert) Rabarim., Callm. & J. Calvo , comb. nov., stat. nov.

— Involucral bracts 3.6-4 mm long; florets c. 20 ................................... 9. H. racemosa (Bojer ex DC.) C. Jeffrey

8. Involucral bracts 2-3 mm long; leaves glabrous to initially arachnoid on adaxial surface ................................. ................................................................3. H. apocynifolia (Baker) Rabarim., Callm. & J. Calvo , comb. nov.

— Involucral bracts 3.7-5.3 mm long; leaves pilose to tomentose-hirsute (rarely glabrous) on adaxial surface .......... 9

9. Involucral bracts (11-)13, 3.7-4.5 mm long .............................................. 4. H. coursii (Humbert) C. Jeffrey

— Involucral bracts 8(-9), 4.4-5.3 mm long .......................... 6. H. madagascarensis Y.L. Peng & Li Bing Zhang