Notothlaspi, commonly called penwiper, is a small genus of flowering plants in the family Brassicaceae (mustard family), order Brassicales. It is endemic to New Zealand, making it one of the country's distinctive alpine plant genera. The genus was described by Joseph Dalton Hooker in 1862, published in Bentham & Hooker's Genera Plantarum.
Plants in Notothlaspi are small, fleshy herbs — either simple or branched — that produce fragrant flowers arranged in terminal racemes or corymbs. The white, spathulate petals sit on wide claws, and the sepals are erect and not saccate. A characteristic fruit type unites the genus: silicles that are laterally compressed, with valves bearing broad wings that exceed the apex. Seeds are numerous, reniform (kidney-shaped), and borne on long, thread-like funicles; cotyledons are incumbent.
The three recognised New Zealand endemic species differ in habit and leaf form. Notothlaspi rosulatum, the type species, is a biennial herb forming a single leafy rosette with obovate-spathulate leaves and relatively large silicles (7–20 mm long). Notothlaspi australe is a perennial that grows as single rosettes or open, loose cushions with broadly ovate leaves. Notothlaspi viretum is also perennial and forms compact, dense cushions with narrow linear leaves.
Etymology
The genus name Notothlaspi was coined by Joseph Dalton Hooker in 1862, published in Genera Plantarum (co-authored with George Bentham). The common name "penwiper" refers to the distinctive broad-winged, flattened silicle fruits, which resemble the cloth pen-wipes used in the nineteenth century.
Distribution
Notothlaspi is endemic to New Zealand, with all three species restricted to the country. The genus is classified as Indigenous (Endemic) in the NZ Flora biostatus system, meaning no species are naturalised introductions.
Ecology
Notothlaspi is characterised in the scientific literature as a specialist alpine genus of New Zealand (Heenan 2019, Phytotaxa 399(3): 248–260). The fleshy, rosulate growth form and compact cushion habit seen across species are adaptations typical of New Zealand's high-altitude herbfields and rocky mountain environments.
Taxonomy Notes
The genus was established by Hooker (Hook.f.) in Bentham & Hooker, Gen. Pl. 90 (1862), with Notothlaspi rosulatum as the type taxon. It belongs to the family Brassicaceae (also treated as Cruciferae), order Brassicales, class Magnoliopsida. A 2019 taxonomic revision by Heenan (Phytotaxa 399(3): 248–260) recognised three species. GBIF lists 2 accepted descendants; NZ Flora lists 3 (including N. viretum Heenan, described in the 2019 revision).
