It is frequently declared that plants are engaged in competition. Plants neither "struggle," "seek," nor "try"; thus, if the word competition is to be used, it must be understood to be entirely passive. At the beginning of chapter 33 on roots,

M Notes # it was stated that roots grow where they can grow. The same can be said of plants. Plants grow where they grow because of various adaptations, which came about through natural selection. Plants growing in arid regions, for example, tend to be grayish in color, thick leaved, thorny, and have sunken stomates. These adaptations allow them to survive in locations lacking in water. The giant Sequoia trees of coastal California occupy a relatively limited area where they have survived in their ecological niche for millions of years. In the long range, they may be on their way to extinction. Some would say that they are holding on long after their time. The ubiquitous dandelion, on the other hand, does not have such limitations. It tolerates a wide range of temperature and moisture conditions; grows well in clay and sandy soils, and in light and shade; and often seems to dominate the landscape.

Plants grow in a variety of environments, some of which are harsh: hot springs, salt flats, icebergs. The commonplace environments are marine, fresh water, and terrestrial.

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