Definition of nucellus in US English:



  • The central part of an ovule, containing the embryo sac.

    • ‘Ovules consisted of an outer integument that surrounded the inner integument to form the micropyle, with the inner integument surrounding the nucellus and embryo sac.’
    • ‘Diboll and Larson report that there are no plasmodesmata connecting the nucellus to the embryo sac.’
    • ‘A nucellar dome has been formed in the massive nucellar cap and the integument has overgrown the nucellus and formed a wide-open micropyle.’
    • ‘Other barriers may also exist because xylem-mobile safranin failed to enter the ovary although the xylem passes around the nucellus and into the stylar tissue.’
    • ‘In addition, the grains were observed to float in water with sacci uppermost, consistent with the suggestion that distally placed sacci serve to orientate the germinal furrow of the pollen grain towards the nucellus of an inverted ovule.’


Late 19th century: modern Latin, apparently an irregular diminutive of nucleus.