Figure 7
Megagametogenesis in Hypericum perforatum. (a) Ovule at stage 3–4 with a sexual and an aposporic embryo sac; Bar=40 μm. (b) Ovary showing several ovules at stage 3–4 with developing round-shaped embryo sacs; Bar=200 μm. (c) Ovule at stage 3–4 bearing two aposporic embryo sacs; Bar=50 μm. (d) A binucleated embryo sac centrally positioned into the chalaza; Bar=80 μm. (e) Ovule at stage 4–5 showing an embryo sac shortly after the first mitotic division (the two nuclei are indicated by arrows); Bar=40 μm. (f) Ovules at stage 6–7 showing cellularising embryo sacs with an extended shape; Bar=200 μm (my, mycropile; ch, chalaza; fu, funiculus; dMs; degenerating megaspores; sES, sexual embryo sac; aES, aposporic embryo sac; v, vacuole).
