Every age has its own dangers. Many seeds never germinate, many seedlings perish because they do not reach soil, or are killed by too much or too little moisture, or by heat or cold, or shade. At the sapling age, the side branches begin to interfere with those of other saplings. Buds are bruised and lower branches broken by thrashing in the wind, and their leaves have less light. Only the upper branches have room and light, and they flourish at the expense of lower ones, which gradually die and are thus pruned off. Some trees naturally grow faster than others, and they attain additional light and room to spread laterally, thus overtopping others which are suppressed and finally killed, beaten in the race for life. If the growth should remain about even so that the trees grew densely packed together, the whole group would be likely to be of a poorer quality, but ordinarily the few outgrow the many and they are called dominant trees. Even then, they still have to struggle against their neighbors, and at this, the large sapling stage, many perish, and of those that survive there are great differences in size. Trees make their most rapid growth in height, and lay on the widest yearly "rings," at the large sapling and small pole age, Fig. 114, p. 263. It is at this stage, too, if the growth is at all dense, that the young trees (poles) clean themselves most thoroly of their branches. The growth in diameter continues to the end of the tree's life, long after the height growth has ceased. When trees become "standards," and reach the limit of height growth, thru their inability to raise water to their tops, their branches must perforce grow sidewise, or not at all. The struggle for life thus takes a new form. How trees are able to raise water as high as they do is still unexplained, but we know that the chief reason why some trees grow taller than others, is due to their ability to raise water. The most remarkable in this respect are the California redwoods, the big trees, and certain eucalypts in Australia. This inability of trees to grow above a certain height results in a flattening of the crown, Fig. 73, and at this stage, the trees struggle against each other by crowding at the side. [Illustration: Fig. 73. Flattened Crown of Red Pine. _U.S. Forest Service._] Inasmuch as trees grow more sensitive to shade with advancing age, the taller trees have the advantage. Each survivor is one of a thousand, and has outlived the others because it is best fitted for the place.