Tobe & Raven, Embryology of Onagraceae (Myrtales) 
675 
Figs 10-18. Longitudinal sections of ovules of some genera at the megaspore tetrad stage (Figs 10-16 
and 18) and at the 2-nucleate embryo sac (es) stage (17), showing the thickness of parietal tissue (pt) 
and the position of a tetrad of megasporos (tm). 10. Fiicbsin jimenczii. 11. Lopezia mcetnosa. 12. Epilobiiiw 
ciliattwi subsp. watsouii. 13. Cnyophyhim rninosissimum. 14. Clnrkia icncUa. 15. Hnuya clcgmts. 16 and 
17. Clarkia helcrandra {'Heterogaura') 18. Gmigyhcarpus fmticulosus. See text for explanation. Scales 
equal 20 pm, 20 pm, 20 pm, 20 pm, 50 pm, 100 pm, 100 pm, 20 pm and 50 pm, respectively. 
