What is found in the junctures of the trees? ( Chapter 1 )

On one side of the river the golden foothill slopes curve up to the strong and rocky Gabilan Mountains, but on the valley side the water is lined with trees— willows fresh and green with every spring, carrying in their lower leaf junctures the debris of the winter’s flooding; and sycamores with mottled, white, recumbent limbs and branches that arch over the pool.