wonderfully long time. "One of the most interesting characteristics of the
woody tissues in relation to the transfer of water is the immediate change
which the cut surface of a stem undergoes upon exposure to the air,
unfitting it for its full conductive work. De Vries has shown that when a
shoot of a vigorous plant, for instance a Helianthus, is bent down under
water, care being taken not to break it even in the slightest degree,
a clean, sharp cut will give a surface which will retain the power of
absorbing water for a long time; while a similar shoot cut in the open
air, even if the end is instantly plunged under water, will wither much
sooner than the first."--Physiological Botany, p. 263.]

[Footnote 2: Physiological Botany, p. 260.]

(6) Let the leaves of a growing plant rest against the window-pane.
Moisture will be condensed on the cold surface of the glass, wherever the
leaf is in contact with it. This is especially well seen in Nasturtium
(Tropæolum) leaves, which grow directly against a window, and leave the
marks even of their veining on the glass, because the moisture is only
given out from the green tissue, and where the ribs are pressed against
the glass it is left dry.

Sometimes the water is drawn up into the cells of the leaves faster than
it can escape into the atmosphere.[1] This is prettily shown if we place
some of our Nasturtium seedlings under a ward-case. The air in the case is
saturated with moisture, so that evaporation cannot take place, but the
water is, nevertheless, drawn up from the roots and through the branches,
and appears as little drops on the margins of the leaves. That this is
owing to the absorbing power of the roots, may be shown by breaking off
the seedling, and putting the slip in water. No drops now appear on the
leaves, but as soon as the cutting has formed new roots, the drops again