ere dew. The surface of the
leaf was not wet all over, and the amount of deposit on any part had no
relation to its exposure to radiation or access to moist air; but the
moisture was collected in little drops, placed at short distances apart,
along the very edge of the leaf. Closer examination showed that the
position of these drops had a close relation to the structure of the
leaf; they were all placed at the points where the veins in the leaf came
to the outer edge, at once suggesting that these veins were the channels
through which the liquid had been expelled. An examination of grass
revealed a similar condition of matters; the moisture was not equally
distributed over the blade, but was in drops attached to the tips of some
of the blades. These drops, seen on vegetation on dewy nights, are
therefore not dew at all, but are an effect of the vitality of the plant.

It is pointed out that the excretion of drops of liquid by plants is no
new discovery, as it has been long well known, and the experiments of Dr.
Moll on this subject are referred to; but what seems strange is that the
relation of it to dew does not seem to have been recognized.

Some experiments were made on this subject in its relation to dew. Leaves
of plants that had been seen to be wet on dewy nights were experimented
on. They were connected by means of an India-rubber tube with a head of
water of about one meter, and the leaf surrounded with saturated air. All
were found to exude a watery liquid after being subjected to pressure for
some hours, and a broccoli leaf got studded all along its edge with
drops, and presented exactly the same appearance it did on dewy nights. A
stem of grass was also found to exude at the tips of one or two blades
when pressure was applied.

The question as to whether these drops are really exuded by the plant, or
are produced in some other way, is considered. The tip of a blade of
grass was put under conditions in which it could not extract moisture
from the surrounding air, and, as the drop grew as rapidly under these
conditions as did those on the unprotected blades, it is concluded that
these drops are really exuded by the plant. Grass was found to get
"dewed" in air not quite saturated.

On many nights no true dew is formed, and nothing but these exuded drops
appear on the grass; and on all nights when vegetation is active, these
drops appear before the true dew; and if the radiation is strong enough
and the supply