Bot. [= F. tercine (Mirbel, 1828), f. F. tiers, tierce, or L. tertius third: see -INE1.] A third integument supposed by some to occur in certain ovules: cf. PRIMINE.
1832. Encycl. Brit. (ed. 7), V. 52, note. The extensible side of the secundine, and even of the tercine or nucleus, soon ceases to increase.
1861. Bentley, Man. Bot. (1870), 322. The embryo-sac is surrounded by a thin layer of cells, which has received the name of tercine.