a. Nat. Hist. [f. Gr. τρίγων-ος (see TRIGON) + -OUS.] = TRIGONAL 2.

1

[1760–88.  J. Lee, Introd. Bot., Gloss., Trigonus caulis, a three-sided stalk.]

2

1821.  W. P. C. Barton, Flora N. Amer., I. 114. Capsule truncate, trigonous.

3

1828.  Stark, Elem. Nat. Hist., I. 259. Dendrocolaptes,… Bill depressed and trigonous at the base.

4

1870.  Hooker, Stud. Flora, 245. Convolvulus arvensis … seeds 4, obtusely 3-gonous.

5