placentationn.
/ˌplas(ə)nˈteɪʃn/, U.S. /ˌplæs(ə)nˈteɪʃ(ə)n/ 1. Botany. The disposition or arrangement of the placenta or placentas in the ovary of a plant.
ΘΚΠ
the world > plants > part of plant > reproductive part(s) > flower or part containing reproductive organs > [noun] > parts of > stamen or pistil > style or pistil and related parts > carpel and placenta > arrangement of placenta
placentation1760
monocarpy1970
1760 J. Lee Introd. Bot. iii. xi. 193 By Placentation is meant the Disposition of the Cotyledons at the Time when the Seed is beginning to grow.
1848 J. Lindley Introd. Bot. (ed. 4) I. 389 The placentation of Water-lilies..Broom-rapes..and Butomads, is equally at variance with the central theory.
1872 C. Darwin Origin of Species (ed. 6) vii. 174 Instances of both marginal and free central placentation.
1914 F. E. Fritsch & E. J. Salisbury Introd. Study Plants xix. 246 The arrangement or placentation of the ovules in this case is said to be axile (e.g. Hyacinth..Snapdragon..).
1951 G. H. M. Lawrence Taxon. Vascular Plants i. iv. 78 A uniovulate placentation in some instances has been derived from parietal placentation of a multicarpellate ovary.
1992 M. Ingrouille Diversity & Evol. Land Plants 133 Others are related to changes in the number of seeds produced and their protection and dispersal: towards different kinds of placentation, the inferior ovary and different fruit types.
2. Zoology. The formation and arrangement of the placenta in the uterus.
ΘΚΠ
the world > life > biology > biological processes > procreation or reproduction > embryo or fetus > membranes, etc., of embryo or fetus > [noun] > placenta > disposition of
placentation1837
1837 Philos. Trans. (Royal Soc.) 127 89 The connexion subsisting between placentation and high cerebral organization may be one of simple coincidence.
1871 Trans. Royal Soc. Edinb. 26 486 Of the mammals, the placentation of which most commonly comes under observation, the sow and the mare also offer well-known examples of the diffused form of placenta.
1880 T. H. Huxley in Proc. Zool. Soc. 650 It would come nearest to the Lemuroidea and the Insectivora, though the non-prehensile pes would separate it from the former, and the placentation from the latter group.
1971 J. Z. Young Introd. Study Man xxx. 423 The sexual cycle and placentation of lemurs are interestingly different from those of other primates.
1995 New Yorker 7 Aug. 57/1 There is evidence now from four studies that placentation does make a difference in twin resemblance.
This entry has been updated (OED Third Edition, June 2006; most recently modified version published online March 2022).
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n.1760