Bot. [in Fr. exogène (De Candolle 1813), mod.L. exōgena, -us (imitating L. indigena, -us) adj., growing on the outside, used in fem. as sb., f. Gr. ἔξω (see EXO-) + γενής born, produced.] A plant whose stem grows by deposit on its outside; opposed to ENDOGEN.
The class of Exogens is identical with that of the Dicotyledons, one of the two main divisions of phanerogamous plants. (But see quot. 1889, and cf. Balfour in Encycl. Brit., IV. 99).
[1830. Lindley, Nat. Syst. Bot., 1. Exogenæ have a distinct deposition of pith, wood, and bark.]
1838. Penny Cycl., X. 128/1. Exogens have an embryo so robust as to be able to spring at once into existence.
1873. Dawson, Earth & Man, vi. 121. Those higher plants which start in life with two seed-leaves, and have stems with distinct bark, wood, and pith—the Exogens.
1889. Chambers’ Cycl., Exogenous Plants, or Exogens, a term applied to dicotyledons by Lindley to express an erroneous view of the mode of stem-thickening from that of monocotyledons, and now wholly disused by botanists.
