Flax embryo development. (A) Cleared seed soon after fertilization. The embryo sac (arrow) encloses the embryo and endosperm and is anchored in the micropylar end (me) of the thick seed coat. (B-O) Scanning electron microscopy of developing flax embryo. (B) Dissected micropylar end of the seed showing endosperm cells (en) surrounding the developing globular embryo (em). (C) Globular embryo with suspensor anchored at the micropylar end. (D) Micropylar sleeve that remains after removal of the globular embryonic suspensor. (E) Globular embryo. (F) Heart embryo. The cotyledon primordia are indicated by "cp". (G) Early torpedo embryo. (H) Late torpedo embryos with pointed cotyledon tips. (I) Cotyledon stage embryo with rounded cotyledon tips. (J) Mature embryo with elongated cotyledons and a short embryonic axis. (K) Higher magnification of the cotyledon (co) and hypocotyl (hy) as indicated by the inset rectangle shown in (J). (L) The radicle tip showing the embryonic root apical meristem (ram). (M) The embryonic shoot apical meristem (sam) and leaf primordia (lp). Mature embryonic (N) cotyledon and (O) hypocotyl in cross-section to show cellular differentiation and storage deposits. Bar = 1 mm (J), 0.1 mm (A, B, G-I, K-O) and 10 μm (C-F).