[mod. f. L. æstīvāt- ppl. stem of æstīvā-re (see ÆSTIVATE), after nouns of action in -TION, as if ad. L. *æstīvātiōn-em. In the Bot. sense it is ad. mod.L. æstīvātio introduced by Linnæus. Lord Bacon spelt estivation, but the techn. spelling is commonly æstivation. As to the pronunciation of æ-, see ÆSTIVAL, and cf. estimation, L. æstimātio.]
† 1. The passing or spending of the summer; summer retreat or residence. Obs.
1625. Bacon, Ess., xlv. 552. Let it be turned to a Grotta, or Place of Shade, or Estiuation.
1731. Bailey, vol. II., Æstivation, a dwelling or residence in a place for the summer time.
1755. Johnson, Estivation, the act of passing the summer.
2. Zool. The act of remaining dormant or torpid during the dry season, or extreme heat of summer; summer-sleep. Opposed to hibernation. Also fig.
1845. Darwin, Voy. of Nat., v. (1879), 99. Within the tropics, the hybernation, or more properly æstivation, of animals is determined not by the temperature, but by the times of drought.
1870. Pall Mall G., 12 Dec., 11. With what we are pleased to call the cold weather Calcutta rouses herself from her æstivation of seven long months.
3. Bot. Internal arrangement of a flower-bud; manner in which the petals are folded up therein before expansion; præfloration. Opposed to vernation, or the arrangement of the leaf-bud (flowers expanding in summer, and leaves in spring).
1830. Lindley, Nat. Syst. Bot., 151. With Malvaceæ they agree in the twisted æstivation of the corolla.
c. 1875. Hulme, Wild Flowers, 6. Meadow Crane’s-Bill.—Calyx of five sepals, imbricate in æstivation.
