The embryo extends almost the length of the megagametophyte (figure 10), and this extension relative to the megagametophyte length is a good index of seed ripening (Dobbs and others 1976; Oliver 1974) (see also table 6). Embryonic cotyledons, which may vary from 3 to 14, are well-differentiated, but the radicle apex is difficult to discern as it is encased by the protective root cap.