it be the ratio vacui; for since not moisture only but air also
is contained in the earth, the plant would be filled not with
juice but with air. But Cesalpino hits upon a third kind of
cause by which juices may be drawn into the plant. Do not
many dry things, he says, in accordance with their nature
attract moisture, as linen, sponge and powder, while others
repel it, as the feathers of many birds and the herb Adiantum,
which are not wetted even when dipped in water; but the
former absorb much water, because they have more in common with it than with air; of this kind Cesalpino thinks those
parts of plants must be, which the nourishing soul employs to
take in food. Therefore these organs are not traversed by a
continuous canal such as the veins in animals, but formed like
the nerves of a fibrous substance; and thus the power of
suction (bibula natura) conveys the moisture continually to
the place, where the principle of internal heat is placed, just as
may be seen in the flame of a lantern, to which the wick
continually conducts the oil. The absorption of the moisture
is also increased by the outer warmth, for which reason plants
grow more vigorously in spring and summer.
That Cesalpino had no suspicion of the use of the leaves in the nutrition of plants appears incontestably from his repeating the Aristotelian idea, that the leaves are only for the protection of young shoots and fruits from air and sun-light; this idea is no result of speculation, but came simply from observing a vineyard in a hot country.
2. First inductive experiments and opening of new points of view in the History of the Theory of the Nutrition of Plants.
All that Aristotle and his school, Cesalpino not excepted, are able to tell us about the phenomena of vegetable life, was the result of the most every-day observations, none of which were critically and exactly tested to ascertain their actual correctness,
