Personal Narrative Of Travels To The Equinoctial Regions Of America During The Years 1799-1804 - Volume 1 - By Alexander Von Humboldt And Aime Bonpland.
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And Vegetation Is Maintained By The Property Which The
Leaves Possess Of Attracting The Water Dissolved In The Atmosphere.
At sunrise, we saw the Zamuro vultures,* (* Vultur aura.) in flocks
of forty or fifty, perched on the cocoa-trees.
These birds range
themselves in files to roost together like fowls. They go to roost
long before sunset, and do not awake till after the sun is above
the horizon. This sluggishness seems as if it were shared in those
climates by the trees with pinnate leaves. The mimosas and the
tamarinds close their leaves, in a clear and serene sky,
twenty-five or thirty-five minutes before sunset, and unfold them
in the morning when the solar disk has been visible for an equal
space of time. As I noticed pretty regularly the rising and setting
of the sun, for the purpose of observing the effect of the mirage,
or of the terrestrial refractions, I was enabled to give continued
attention to the phenomena of the sleep of plants. I found them the
same in the steppes, where no irregularity of the ground
interrupted the view of the horizon. It appears, that, accustomed
during the day to an extreme brilliancy of light, the sensitive and
other leguminous plants with thin and delicate leaves are affected
in the evening by the smallest decline in the intensity of the
sun's rays; so that for vegetation, night begins there, as with us,
before the total disappearance of the solar disk. But why, in a
zone where there is scarcely any twilight, do not the first rays of
the sun stimulate the leaves with the more strength, as the absence
of light must have rendered them more susceptible?
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