In its first ten years space exploration exploded from paper plans into a force that involved most of the industrial nations and affected an entire planet. In spite of this tremendous growth, it seems likely that the next decade will be even more revolutionary—not because a few men will reach the moon and others will prepare to visit the planets, but because of what space will do for the billions who stay behind.
Lateral growth in trees frequently begins later than growth in height, but the period of lateral growth is longer. Rates of lateral growth likewise are low at the outset, increasing after a few weeks and then diminishing. In view of the long annual period of lateral growth in trees, deleterious environmental conditions may exercise a pronounced effect on growth. In the wood of trees of temperate regions, narrow and wide growth rings may be observed, marking years characterized by unfavorable and favorable conditions for growth.
Growth Cycles.—Longitudinal and lateral (diametral) growth do not proceed continuously, but rather are cyclical phenomena with periods of growth activity alternating with periods of relative inactivity. One of the best illustrations of the periodic nature of growth in large woody stems is to be found in the annual ring pattern which characterizes the wood of trees of temperate regions. It has been suggested recently that even in the apparently ever-growing trees of the tropical rain forest, cambial growth is not a continuous process.
In its first ten years space exploration exploded from paper plans into a force that involved most of the industrial nations and affected an entire planet. In spite of this tremendous growth, it seems likely that the next decade will be even more revolutionary—not because a few men will reach the moon and others will prepare to visit the planets, but because of what space will do for the billions who stay behind.