micropylen.

1821 tr. A. P. de Candolle & K. Sprengel Elements Philos. Plants 79 In the seeds of many of the Leguminous plants, a small cavity appears under the umbilicus, called micropyle, but its use is unknown.

1830 J. Lindley Introd. Nat. Syst. Bot. 181 The woody shell of the seed of Sapoteae is certainly testa,..as is proved by the presence of the micropyle upon it.

1875 A. W. Bennett & W. T. T. Dyer tr. J. von Sachs Text-bk. Bot. 429 It [sc. the pollen] then forces itself into the micropyle and advances as far as the embryo-sac.

1905 I. B. Balfour tr. C. E. von Goebel Organogr. Plants II. 615 The micropyle in all porogamous plants evidently conducts the pollen-tube.

1950 P. Maheshwari Introd. Embryol. Angiosperms vi. 183 The tube may enter the ovule either through the micropyle or by some other route. The former is the usual condition and is known as porogamy.

1995 Jrnl. Ecol. 83 772/1 Orientation may affect moisture uptake by the seed if different orientations expose the region of moisture uptake (e.g. micropyle, hilum) to microsites within the soil that vary in water availability.

1855 Proc. Royal Soc. 7 170 In the act of impregnation one or more..spermatozoids pass into the micropyle.

1858 Trans. Linn. Soc. 22 206 Leukart..clearly shows that the micropyle..may occur at either or both poles of the egg.

1893 J. Tuckey tr. B. Hatschek Amphioxus 41 This..explains how it is that without the formation of a micropyle the spermatozoon can force its way into the egg.

1969 R. F. Chapman Insects xv. 294 There are rings of cells in the follicular epithelium which..produce the cap..and the micropyles.

1989 B. Alberts et al. Molecular Biol. Cell (ed. 2) xv. 871 Fish eggs have a small channel, called the micropyle, through which sperm must pass in single file.

1994 Proc. National Acad. Sci. U.S.A. 91 11225/2 Perhaps only long sperm contain surface receptors necessary for sperm entry into the micropyle.