Lobelia monostachya
Genus: Lobelia section Revolutella.
Status: Extinct.
Range: O'ahu, southern Ko'olau Mountains, mesic forest, 1,000-1,200 m.
Growth form: Subshrub, 0.15-0.25 m tall.
Etymology: monostachya refers to this species having a single raceme in contrast to its sister variant, paniculata (now Lobelia dunbariae) which is 2-6-branched at the base. Oddly an unbranched inflorescence is not different than the other sister variant at the time the name was coined, Lobelia hillebrandii var. typica which also has an unbranched inflorescence.
First described as Hillebrand's Lobelia neriifolia var. γ. The name Lobelia neriifolia has some confusion due to 1) the pre-existence of this binomial for another plant and 2) Hillebrand describing a completely different plant using this name. Rock claimed Hillebrand's L. neriifolia and variants were actually not the same species as Gray's original neriifolia, thus Rock changed the name of Hillebrand's neriifolia to L. hillebrandii. Rock also gave the var. γ the subspecific name monostachya. This was segregated and elevated to the specific rank L. monostachya by Lammers ex. Wagner et al. 1990.
How to identify: This Revolutella from O'ahu has magenta flowers like L. niihauensis, but L. monostachya occurs in the southern Ko'olau mountains whereas L. niihauensis is from the northern Wai'anae mountains. Its leaf undersides are glabrous. Different from the other Lobelia on O'ahu it is leafy on the upper half of its stem whereas the other species from O'ahu have apical rosettes.
Sources:
- Hillebrand, 1888 (as Lobelia neriifolia var. γ);
- Rock, 1919 (as Lobelia hillebrandii var. monostachya);
- Wimmer, 1953 (as Lobelia hillebrandii var. monostachya);
- Wagner et al., 1990.