Pollen-tube growth and development of the ovary and ovule at the time of pollination (the end of March) in Alnus.(A) Female inflorescence consisting of ≈300 female flowers. (B) A pistil at the time of pollination. (C) Longitudinal section (LS) of the part of the ovary indicated with a rectangle (asterisk) in B.(D) LS of the part of the style indicated with a rectangle (double asterisks) in B, showing that cells of the style contain many starchy grains. (E) Two stigmas and a style, indicated by a rectangle (triple asterisk) in B, showing pollen tubes (arrows). (F) Part of E magnified to show the pollen tubes (arrows) lying zigzag in the style. (G) A diagram illustrating pollen-tube growth in the pistil soon after pollination. Bold curved lines show pollen tubes, and gray shading shows cells with many starch grains. ova, ovary; pr, ovule primodium; sg, stigma; sy, style. (Scale bar, 5 mm in A, 0.5 mm in B, 200 μmin E, 100 μmin C and F, and 50 μmin D.)