Twiggy shrub 2–3 m tall; stipules not found; leaves decussate on young stems or crowded in pairs at tips of short dense lateral shoots without measurable internodes, those of previous seasons deciduous; petiole very short, eglandular; lamina linear (10–23 mm long, 2–5 mm wide, mostly about 5 times as long as wide), adaxially glabrous at maturity, abaxially densely and persistently sericeous, mostly bearing 2 small impressed glands on abaxial surface in proximal half set in from margin. Plants dioecious; staminate plants unknown; pistillate plants known only from material with old flowers and fruits. Pistillate plants: Inflorescence with the flowers borne singly in axils of full-sized leaves, or above the scars from deciduous leaves; bracts and bracteoles minute (? or absent); pedicels sessile. Flowers probably radially symmetrical in all whorls. Sepals eglandular; petals probably white or possibly pale greenish yellow, spatulate, entire, abaxially densely sericeous; staminodes 10, inserted around outer edge of disc, short and bearing rudimentary unopened anthers, glabrous; gynoecium 2-carpellate, both carpels fertile, connate their length in ovary; styles 2, distinct, alike, each distally bifid into 2 long slender stigmas. Fruit dry, breaking apart at maturity into 2 samaras separating from a short 2-sided torus; samara orbicular with the lateral wing well developed, membranous with a prominent reticulum of arching anastomoses, continuous at base, continuous at apex or shallowly to deeply notched, the dorsal wing large and resembling one side of the lateral wing; fruit subtended by a large fleshy 2-lobed disc; carpophore absent. Chromosome number unknown.
One species, D. microphylla, known only from shrubby vegetation on sand dunes near the southwestern coast of Madagascar, in the regions Atsimo-Andrefana and Androy. [map] — Regional key to genera: Madagascar.
Digoniopterys is most notable for its deeply bifid styles; nothing like them exists in any other genus of the family. The exact nature of those styles will not be known until material is collected with young flowers, but even with the old material at hand there does not seem to be much doubt that the styles really do branch, and those branches seem likely to be stigmatic their whole length. The genus is also interesting for its breeding system—whereas its close relatives (Madagasikaria, Microsteira, Rhynchophora) all seem likely to be functionally dioecious with the pistillate flowers bearing large stamens with anthers that open to release inaperturate pollen, in Digoniopterys the staminodes in the pistillate flowers are clearly rudimentary and do not open to release anything. The samaras in Digoniopterys bear a strong resemblance to those of Calcicola sericea and Mascagnia spp.
Reference: Arènes, 1950.
Etymology: The name Digoniopterys comes from the Greek words for two (di-), angle (gonia), and wing (pteron). It refers to the fact that the samara bears two wings, lateral and dorsal, at right angles to each other.
Photos: D. microphylla (habitat, habit)
Drawing: D. microphylla