Constitution of Amphicribral Vascular Bundles in Capsule
De Bary observed that amphicribral vascular bundles are apparently rare in angiosperms. Their occurrence in diocotyledons has been reported in flowers, fruit, ovules, and leaves (Eames and MacDaniels)/stamens (Leinfellner), and pith. Two adjacent vascular bundles with their xylary strands facing each other join. Xylem joins xylem and the phloem becomes continuous around the resulting xylem strand to form an amphicribral bundle. In the capsule the number of amphicribral bundles varies with the plant, but the number entering the capsule is generally equal to the number of placentae and stigmatic rays. Each distal collateral derivative of an amphicribral placental bundle bifurcates its placenta, and each branch fuses with a comparable adjacent bundle. The resulting product supplies the stigmatic rays with numerous small bundles. The phloem fibers which form characteristic caps on the vascular bundles were not observed on the bundles supplying the ovules, valves, or stigmatic rays.