Of the following genera: sycamore, cottonwood, alder, which genus has seed dispersal over the greatest distance and what seed structure permits such dispersal? In your choice, cite evidence in its distribution. 2. How is it that a small tree such as palo verde (Cercidium floridum) can grow as microphyll woodlands in desert washes in areas where rainfall is less than 4 inches a year? 3. Why is grazing damage to plant cover more severe on islands than on the mainland? 4. Why do desert plants growing near lake beds also grow near sea coasts?

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