A Grammatical Dictionary of Botanical Latin

trigonus,-a,-um (adj.A), triquetrus,-a,-um (adj.A), trigonalis,-e (adj.B): trigonous, “having three angles and three plane faces, as the stem of Carex acuta” (Lindley); three-cornered, having three angles and three plane faces between them (not a pyramid, but an elongate solid, such as an angled-column, such as a petiole); see -gonus,-a,-um (adj.A); = Latin: triangulus,-a,-um (adj.A); see triangular (with three angles):

- culmis tenuibus, trigonis, angulis rotundatis et lateribus plano-convexis, with culms thin, trigonous, with the angles rounded and the sides plano-convex.

- foliis decussatis trigonis mucronulatis sessilibus glanduloso-tuberculatis (F. Mueller), with the leaves decussate, trigonous, mucronulate, sessile, glandulose-tuberculate [note here the “glandules” are swellings: tuberculate or pustulate swellings].