The region of the chorion through which sperm gain access to the egg, the micropyle
, is not adhesive.
trifurca stems and ovules (whether single or in clusters) facilitates pollen capture by creating an aerodynamic "singularity" (i.e., a unique region) around the micropyle
. It should also be noted that the radial clustering of ovules results in the presentation of one or more ovules toward an optimal aerodynamic direction regardless of the direction of ambient wind.
(1998) and Gelbart and von Aderkas (2002) provide a full summary and shows the considerable diversity within a very consistent cone and cone scale morphology, i.e., two ovules, their micropyles directed towards the cone axis, borne on the adaxial surface of an ovuliferous scale itself in the axil of a bract, to make a compound structure in accordance with Florin's model.
the micropyle of the exposed ovule, which ancestrally has produced a drop of secreted water.
In the case of external fertilization in teleosts, spermatozoa reach the egg plasma membrane through a narrow micropyle
that has been perforated in the chorion; the sperm lack an acrosome.
General egg sculpture disappears in the side where micropyle
takes place (Fig.
Herring sperm become motile upon physical contact with the micropyle
region of the egg chorion, and both [K.sup.+] and [Na.sup.+] ions have been implicated in this initiation of sperm motility (Yanagimachi and Kanoh, 1953; Yanagimachi, 1956; 1957; Yanagimachi et al., 1992).