CoachMaking a seed takes two distinct steps:
- pollination: a pollen grain travels from a stamen to the top of a pistil — carried by an insect (Proposition 16.3) or by the wind;
- fertilization: the landed grain grows a fine tube down through the pistil; through it, the male cell reaches an ovule and joins its egg cell.
Pollination is the journey; fertilization is the meeting.
示例
Example 31.4 (Why unvisited flowers fall)
Remark 16.5’s orchard rule now has its mechanism: no visit, no pollen on the pistil; no pollen, no tube, no fertilization; and an unfertilized flower withers whole — no swelling pistil, no cherry. The missing step was invisible, a cell’s journey down a tube — but the empty branch in July is visible enough.