Helen Butler, age 12, of Orange, Calif., for her question:
Which part of a cone makes a pine tree?
The ground beneath a spreading pine tree is carpeted with fallen needles, and here and there we find a few woody brown cones. Perhaps you think that the fallen cones are seeds. But you cannot coax one of them to grow a new pine tree. For the pinecones are the cradles of the seeds and not the seeds themselves.
Most of the world's stately trees bear seeds encased in tough coats or hard shells. Each little seed must burst its wrappings in order to sprout its roots. The cone bearing trees produce seeds that have no crusty outer coverings and are classified as gymnosperms or naked seed plants. This seems strange when you recall that the seeds of the pine tree are produced inside a tough woody come. However, the seeds themselves are not protected by tough overcoats.
The handsome pine tree is clothed in dense foliage that looks somewhat like thick green fur. It is an evergreen that wears its leafy needles through all the changing Seasons. At the ends of a few twigs there are clusters of scaly brown cones. These are the ovulate cones, and a few of them are always present on the tree. In early spring, the tree produces a crop of small staminate cones. They grow in clusters near the base of new twigs and last only a few weeks.
Staminate and ovulate cones both are necessary to produce a new generation of pine trees. The small staminate cones produce pollen cells, the ovulate cones produce egg cells and shelter the developing seeds. In early spring a staminate cone produces a pair of pollen sacs under each of its scales. Their work is completed in May or early June. Then the scales open and the pollen is released into the breezy air. For a time the ground and the surrounding forest are clouded with the dusty yellow pollen of the pine tree.
Meantime the ovulate cones have produced egg cells under their cones. Some of the wind blown pollen falls between their scales. Then the brown ovulate cones close their scales and wait. It takes two years for the pollen and egg cells to unite and form fertilized seeds, and the closed cones stay on the tree for two years after pollination. At last the seeds are ready. The woody brown ovulate cones part their scales, the seeds fall out and soon the cones also fall to the ground. A few lucky seeds will find a suitable place and grow into new pine trees.
The small staminate cones wither and fall in mid summer. The larger ovulate cones stay on the tree for several years. They produce the egg cells and shelter the developing seeds, and when at last they fall their work is done. Their seeds have left home and lie scattered on the forest floor. Each seed took with it a fragment of woody scale to help it parachute for some distance through the air. If it lands on unfriendly soil it may wait for two or more years before it tries to start growing.