Paxistima is a small genus of two species of low, evergreen shrubs in the family Celastraceae (the bittersweet family), native to North America. Commonly known as mountain-lovers, these plants are characterized by opposite, simple, leathery (coriaceous) leaves with finely toothed (serrulate to crenulate) margins, short petioles, and small caducous stipules. The plants are glabrous throughout and often produce subterranean rhizomes, sometimes with adventitious roots on lower portions of the stems.
Flowers are small and inconspicuous, borne singly or in reduced axillary cymes. They are 4-merous, with reddish-brown petals slightly longer than the calyx lobes, and four stamens inserted on the edge of a broad nectariferous disk. The ovary is 2-carpellate and 2-loculed, sunken into the center of the disk. Fruits are oblong capsules containing one or two seeds, each enclosed in a membranous white aril.
The two species occupy very different ranges within North America: Paxistima canbyi (Canby's mountain-lover) is an uncommon shrub restricted to the Appalachian region of the eastern United States, while Paxistima myrsinites (Oregon boxleaf) is widespread across western North America.
Etymology
The name Paxistima is thought to derive from the Greek pachys (thick) and stigma, in reference to a morphological feature of the flower. The generic name has a complex nomenclatural history, having been spelled in four different ways (including Pachistima and Pachystima); Paxistima is now accepted as the correct orthography.
Distribution
The genus contains two geographically disjunct species in North America. Paxistima canbyi is restricted to the Appalachian Mountains and adjacent areas of the eastern United States, where it is considered uncommon. Paxistima myrsinites (Oregon boxleaf) is widespread across western North America, ranging from the Rocky Mountains to the Pacific Coast.
Taxonomy Notes
Paxistima belongs to the family Celastraceae and comprises exactly two accepted species. The genus has a complex nomenclatural history, with four different spellings recorded in the literature (Paxistima, Pachistima, Pachystima, and one other variant); Paxistima is now recognized as the correct spelling. GBIF records the genus as accepted with 2 accepted descendants.
